CRUD Operations using JPA

I will show how to perform four basic functions, create, read, update and delete (CRUD) on relational database application by using JPA in this post.

I only include two programs in the following. Full source codes can be cloned from https://github.com/henry416/jpatest.
1) Student.java: to define a new entity class;
2) StudentTest.java: to perform CRUD operations;

1. Entity Class: Student.java

package henry416.domain;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Student {
	@Id
	private int id;

	private String name;
	
	private double gpa;
	
	public Student() {}

	public Student(int id) {
		this.id = id;
	}
	
	public Student(int id, String name, double gpa) {
		this.id = id;
		this.name = name;
		this.gpa = gpa;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
	
	public double getGpa() {
		return gpa;
	}
	
	public void setGpa(double gpa) {
		this.gpa = gpa;
	}

	@Override
	public String toString() {
		return "Student [id=" + id + ", name=" + name + ", gpa="
				+ gpa + "]";
	}

}

2. CRUD Operations: StudentTest.java

package henry416.jpa;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;

import henry416.domain.Student;

public class StudentTest {

	private EntityManager manager;

	public StudentTest(EntityManager manager) {
		this.manager = manager;
	}
 
	public static void main(String[] args) {
		EntityManagerFactory factory = Persistence.createEntityManagerFactory("persistenceUnit");
		EntityManager manager = factory.createEntityManager();
		StudentTest test = new StudentTest(manager);

		EntityTransaction tx = manager.getTransaction();
		System.out.println("1. create student records");
		tx.begin();
		try {
			test.createStudents();
		} catch (Exception e) {
			e.printStackTrace();
		}
		tx.commit();

		System.out.println("2. read student records");
		test.readStudents();

		System.out.println("3. update a student record");
		tx.begin();
		try {
			test.updateStudent();
		} catch (Exception e) {
			e.printStackTrace();
		}
		tx.commit();		

		System.out.println("4. delete a student record");
		tx.begin();
		try {
			test.deleteStudent();
		} catch (Exception e) {
			e.printStackTrace();
		}
		tx.commit();		
		
		System.out.println("5. delete all student records");
		tx.begin();
		try {
			test.deleteStudents();
		} catch (Exception e) {
			e.printStackTrace();
		}
		tx.commit();		
		
		System.out.println("=> done");
	}

	private void createStudents() {
		// insert a few records
		manager.persist(new Student(1,"Jack Jackson",3.28));
		manager.persist(new Student(2,"Tom Thomson",3.56));
		manager.persist(new Student(3,"Dave Davison",3.65));
		manager.persist(new Student(4,"Neil Nelson",3.56));
		manager.persist(new Student(5,"Mark Markson",3.78));		
	}

	private void readStudents() {
		List<Student> resultList = manager.createQuery("Select s From Student s order by s.id", Student.class).getResultList();
		System.out.println("num of students:" + resultList.size());
		for (Student next : resultList) {
			System.out.println("=> " + next);
		}
	}

	private void updateStudent() {
		// update a student record
		Student stu = manager.find(Student.class, 2);
        	if (stu != null) {
                  System.out.println("from => "+stu);  
        	  stu.setName("Thomas Thomson");
                  stu.setGpa(3.99);
                  System.out.println("to => "+stu);
        	}
	}
	
	private void deleteStudent() {
		// delete ONE record
		Student stu = manager.find(Student.class, 2);
		System.out.println("remove=> "+stu);
		if (stu != null) {
		   manager.remove(stu);
		}

	}
	
	private void deleteStudents() {
		// delete all records
		int deletedCount = manager.createQuery("DELETE FROM Student").executeUpdate();
		System.out.println("total num of records removed => "+deletedCount);
	}
}

3. Result

The following is the execution results:

1. create student records
2. read student records
num of students:5
=> Student [id=1, name=Jack Jackson, gpa=3.28]
=> Student [id=2, name=Tom Thomson, gpa=3.56]
=> Student [id=3, name=Dave Davison, gpa=3.65]
=> Student [id=4, name=Neil Nelson, gpa=3.56]
=> Student [id=5, name=Mark Markson, gpa=3.78]
3. update a student record
from => Student [id=2, name=Tom Thomson, gpa=3.56]
to => Student [id=2, name=Thomas Thomson, gpa=3.99]
4. delete a student record
remove=> Student [id=2, name=Thomas Thomson, gpa=3.99]
5. delete all student records
total num of records removed => 4
=> done

Standalone JPA Project Using Java SE: A Maven Way

In this post, I will show how to create a simple JPA application by using maven and Java SE JDK. All the other libraries will be taken care of by the remote repository in maven, which includes eclipselink and embedded derby db.

I will be focusing on how to use maven to generate, what project structure and programs created, how to execute the application, how to verify the database objects, and what targets can be deployed.

I hope this will help you get started, especially without using any IDEs like Eclipse, Netbean etc.

I won’t go to explain what JPA is. There are many resources and books available.

1. Generate JPA App in Seconds

Make sure to enter ’46′ as artifactID (46 is for com.github.lalyos:standalone-jpa-eclipselink-archetype) when asked in the following:

mvn archetype:generate -DgroupId=henry416 -DartifactId=test1

.................

Choose a number or apply filter (format: [groupId:]artifactId, case sensitive contains): 354: 46
Choose com.github.lalyos:standalone-jpa-eclipselink-archetype version: 
1: 0.0.1
2: 0.0.2
Choose a number: 2: 2
[INFO] Using property: groupId = henry416
[INFO] Using property: artifactId = test1
Define value for property 'version':  1.0-SNAPSHOT: : 
[INFO] Using property: package = henry416
Confirm properties configuration:
groupId: henry416
artifactId: test1
version: 1.0-SNAPSHOT
package: henry416
 Y: : 
[INFO] ----------------------------------------------------------------------------
[INFO] Using following parameters for creating project from Archetype: standalone-jpa-eclipselink-archetype:0.0.2
[INFO] ----------------------------------------------------------------------------
[INFO] Parameter: groupId, Value: henry416
[INFO] Parameter: artifactId, Value: test1
[INFO] Parameter: version, Value: 1.0-SNAPSHOT
[INFO] Parameter: package, Value: henry416
[INFO] Parameter: packageInPathFormat, Value: henry416
[INFO] Parameter: version, Value: 1.0-SNAPSHOT
[INFO] Parameter: package, Value: henry416
[INFO] Parameter: groupId, Value: henry416
[INFO] Parameter: artifactId, Value: test1
[INFO] project created from Archetype in dir: /home/henry/Test/jpatest/test1
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1:42.092s
[INFO] Finished at: Thu Mar 06 21:10:38 EST 2014
[INFO] Final Memory: 10M/25M
[INFO] ------------------------------------------------------------------------

2. Project Structures Generated

henry@brimley:~/Test/jpatest/test1$ ls -ld $(find .)
drwxr-xr-x 3 henry henry 4096 2014-03-06 22:37 .
-rw-r--r-- 1 henry henry   70 2014-03-06 21:10 ./ij.properties
-rw-r--r-- 1 henry henry 1185 2014-03-06 21:10 ./pom.xml
-rwx------ 1 henry henry   60 2014-03-06 21:10 ./run.sh
-rwx------ 1 henry henry  107 2014-03-06 21:10 ./show-derby.sh
drwxr-xr-x 3 henry henry 4096 2014-03-06 21:10 ./src
drwxr-xr-x 4 henry henry 4096 2014-03-06 21:10 ./src/main
drwxr-xr-x 3 henry henry 4096 2014-03-06 21:10 ./src/main/java
drwxr-xr-x 4 henry henry 4096 2014-03-06 21:10 ./src/main/java/henry416
drwxr-xr-x 2 henry henry 4096 2014-03-06 21:10 ./src/main/java/henry416/domain
-rw-r--r-- 1 henry henry  928 2014-03-06 21:10 ./src/main/java/henry416/domain/Department.java
-rw-r--r-- 1 henry henry  992 2014-03-06 21:10 ./src/main/java/henry416/domain/Employee.java
drwxr-xr-x 2 henry henry 4096 2014-03-06 21:10 ./src/main/java/henry416/jpa
-rw-r--r-- 1 henry henry 1597 2014-03-06 21:10 ./src/main/java/henry416/jpa/JpaTest.java
drwxr-xr-x 3 henry henry 4096 2014-03-06 21:10 ./src/main/resources
drwxr-xr-x 2 henry henry 4096 2014-03-06 21:10 ./src/main/resources/META-INF
-rw-r--r-- 1 henry henry 1205 2014-03-06 21:10 ./src/main/resources/META-INF/persistence.xml

The source codes you may be interested in the following separate links:
./pom.xml
./src/main/resources/META-INF/persistence.xml
./src/main/java/henry416/domain/Department.java
./src/main/java/henry416/domain/Employee.java
./src/main/java/henry416/jpa/JpaTest.java

3. Test Run

henry@brimley:~/Test/jpatest/test1$ cat run.sh
mvn compile exec:java -Dexec.mainClass=henry416.jpa.JpaTest

henry@brimley:~/Test/jpatest/test1$ chmod 700 *.sh

henry@brimley:~/Test/jpatest/test1$ ./run.sh 
[INFO] Scanning for projects...
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building test1 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ test1 ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 1 resource
[INFO] 
[INFO] --- maven-compiler-plugin:2.5.1:compile (default-compile) @ test1 ---
[WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent!
[INFO] Compiling 3 source files to /home/henry/Test/jpatest/test1/target/classes
[INFO] 
[INFO] >>> exec-maven-plugin:1.2.1:java (default-cli) @ test1 >>>
[INFO] 
[INFO] <<< exec-maven-plugin:1.2.1:java (default-cli) @ test1 <<<
[INFO] 
[INFO] --- exec-maven-plugin:1.2.1:java (default-cli) @ test1 ---
num of employess:2
next employee: Employee [id=3, name=Captain Nemo, department=java]
next employee: Employee [id=2, name=Jakab Gipsz, department=java]
.. done
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 27.590s
[INFO] Finished at: Thu Mar 06 21:15:27 EST 2014
[INFO] Final Memory: 24M/61M
[INFO] ------------------------------------------------------------------------

4. Result

henry@brimley:~/Test/jpatest/test1$ cat show-derby.sh 
mvn dependency:copy-dependencies
java -cp 'target/dependency/*' org.apache.derby.tools.ij -p ij.properties

henry@brimley:~/Test/jpatest/test1$ ./show-derby.sh 
[INFO] Scanning for projects...
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building test1 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-dependency-plugin:2.8:copy-dependencies (default-cli) @ test1 ---
[INFO] Copying eclipselink-2.2.1.jar to /home/henry/Test/jpatest/test1/target/dependency/eclipselink-2.2.1.jar
[INFO] Copying derbytools-10.8.2.2.jar to /home/henry/Test/jpatest/test1/target/dependency/derbytools-10.8.2.2.jar
[INFO] Copying derby-10.8.2.2.jar to /home/henry/Test/jpatest/test1/target/dependency/derby-10.8.2.2.jar
[INFO] Copying javax.persistence-2.0.3.jar to /home/henry/Test/jpatest/test1/target/dependency/javax.persistence-2.0.3.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 5.026s
[INFO] Finished at: Thu Mar 06 21:17:51 EST 2014
[INFO] Final Memory: 8M/21M
[INFO] ------------------------------------------------------------------------
ij version 10.8
CONNECTION0* - 	jdbc:derby:simpleDb
* = current connection
ij> show schemas;
TABLE_SCHEM                   
------------------------------
APP                           
NULLID                        
SQLJ                          
SYS                           
SYSCAT                        
SYSCS_DIAG                    
SYSCS_UTIL                    
SYSFUN                        
SYSIBM                        
SYSPROC                       
SYSSTAT                       
TEST1                         

12 rows selected
ij> select * from TEST1.DEPARTMENT;
ID                  |NAME                
-----------------------------------------
1                   |java                

1 row selected
ij> select * from TEST1.EMPLOYEE;
ID                  |NAME                |DEPARTMENT_ID       
--------------------------------------------------------------
3                   |Captain Nemo        |1                   
2                   |Jakab Gipsz         |1                   

2 rows selected
ij> exit;

5. Deployment Target

henry@brimley:~/Test/jpatest/test1/target$ ls -ld $(find .)
drwxr-xr-x 4 henry henry    4096 2014-03-06 21:17 .
drwxr-xr-x 4 henry henry    4096 2014-03-06 21:15 ./classes
drwxr-xr-x 4 henry henry    4096 2014-03-06 21:15 ./classes/henry416
drwxr-xr-x 2 henry henry    4096 2014-03-06 21:15 ./classes/henry416/domain
-rw-r--r-- 1 henry henry    1691 2014-03-06 21:15 ./classes/henry416/domain/Department.class
-rw-r--r-- 1 henry henry    1888 2014-03-06 21:15 ./classes/henry416/domain/Employee.class
drwxr-xr-x 2 henry henry    4096 2014-03-06 21:15 ./classes/henry416/jpa
-rw-r--r-- 1 henry henry    3080 2014-03-06 21:15 ./classes/henry416/jpa/JpaTest.class
drwxr-xr-x 2 henry henry    4096 2014-03-06 21:15 ./classes/META-INF
-rw-r--r-- 1 henry henry    1205 2014-03-06 21:15 ./classes/META-INF/persistence.xml
drwxr-xr-x 2 henry henry    4096 2014-03-06 21:17 ./dependency
-rw-r--r-- 1 henry henry 2671577 2014-03-06 21:17 ./dependency/derby-10.8.2.2.jar
-rw-r--r-- 1 henry henry  174969 2014-03-06 21:17 ./dependency/derbytools-10.8.2.2.jar
-rw-r--r-- 1 henry henry 6412045 2014-03-06 21:17 ./dependency/eclipselink-2.2.1.jar
-rw-r--r-- 1 henry henry  126856 2014-03-06 21:17 ./dependency/javax.persistence-2.0.3.jar

6. Run As Java Application

henry@brimley:~/Test/jpatest/test1$ cd target/classes
henry@brimley:~/Test/jpatest/test1/target/classes$ java -cp '../dependency/*' henry416.jpa.JpaTest
num of employess:2
next employee: Employee [id=3, name=Captain Nemo, department=java]
next employee: Employee [id=2, name=Jakab Gipsz, department=java]
.. done

7. Summary

By using maven, it’s pretty easy to create a project structure for a JPA application (Kudos to you Lajos Papp). By replacing those POJO entity classes with your own classes, modifying persistence.xml to your local database and pom.xml to the latest maven repository, you can code a real world java application in JPA. I hope this will make JPA programming more interesting.

Undocumented SQL Server 2012 Express LocalDB

As a developer of Microsoft Visual Studio, SQL Server 2012 Express LocalDB probably has gotten onto your machine without your notice. I will document some of my exploration on LocalDB in this post.

Installation and Location

There are three ways to get LocalDB onto your machines:

  1. Install together when installing Microsoft Visual Studio 2013 (this is my case);
  2. Install by using SqlLocalDB.msi found in SQL Server 2012 Express
  3. Install by downloading from Microsoft Download Centre directly (here).

The installation location is default to C:\Program Files\Microsoft SQL Server\110\LocalDB\Binn where sqlserv.exe is the main application.

The tools (utilities) to operate the LocalDB are SqlLocalDB, SQLCMD and bcp which are located at C:\Program Files\Microsoft SQL Server\110\Tools\Binn. Make sure to include it into your PATH.

SqlLocalDB

This is the utility to administrate the localdb instances.

  • to get help: sqllocaldb -?
  • to print the version: sqllocaldb versions
  • to create an instance: sqllocaldb create “YourInstanceName”
  • to delete an instance: sqllocaldb delete “YourInstanceName”
  • to start an instance: sqllocaldb start “YourInstanceName”
  • to stop an instance: sqllocaldb stop “YourInstanceName”
  • to share an instance: sqllocaldb share “YourInstanceName”
  • to unshared an instance: sqllocadbl unshare “YourInstanceName”
  • to list all your instances: sqllocaldb info
  • to list the status of an instance: sqllocaldb info “YourInstanceName”
  • to set the trace on and off: sqllocaldb trace on|off

If you’ve used VS 2013 to connect to LocalDB, VS 2013 would have created an instance for you (in my case is v11.0).

Even your instance is stopped, it will be auto-started when you try to connect to it first time either via VS 2013 or SQLCMD.

SQLCMD, BCP, process ‘sqlservr’

Both SQLCMD and BCP are well documented. The only difference between LocalDB and SQL server is that we need to put a bracket ‘()’ to indicate it is a LocalDB instead of hostname for the named instance like:

sqlcmd -S ‘(LocalDB)\v11.0′

This is also applied to SSMS and VS 2013 connections. There is only one process “sqlservr” related to LocalDB. It is very lightweighted by using about 12MB RAM on my machine.

Some Examples

The following is executed in powershell:

Windows PowerShell
Copyright (C) 2013 Microsoft Corporation. All rights reserved.

PS C:\Users\henry> sqllocaldb info
Projects
v11.0
PS C:\Users\henry> sqllocaldb info "v11.0"
Name:               v11.0
Version:            11.0.3000.0
Shared name:
Owner:              PolarBear\henry
Auto-create:        Yes
State:              Stopped
Last start time:    12/31/2013 2:37:39 PM
Instance pipe name:
PS C:\Users\henry> sqllocaldb start "v11.0"
LocalDB instance "v11.0" started.
PS C:\Users\henry>  ps | where-object {$_.ProcessName -match 'sqlservr'}

Handles  NPM(K)    PM(K)      WS(K) VM(M)   CPU(s)     Id ProcessName
-------  ------    -----      ----- -----   ------     -- -----------
    492      20    67780      17140   311     3.83   2248 sqlservr


PS C:\Users\henry> sqllocaldb stop "v11.0"
LocalDB instance "v11.0" stopped.
PS C:\Users\henry> sqlcmd -S "(LocalDB)\v11.0"
1> use test
2> go
Changed database context to 'test'.
1> select count(*) from HR.Employees
2> go

-----------
          9

(1 rows affected)
1> shutdown
2> go
Server shut down by request from login PolarBear\henry.
1> exit
PS C:\Users\henry>

Sharing or Not

From A TechNet Article
When sharing a SqlLocalDB instance with a non-owner, you must re-start the instance for the other users to be able to see the instance you have shared. A non-owner cannot start an instance, so if you are going to share an instance with other users who can access your machine, you also need to be sure it has been started. When you create an instance you can do this as follows:

sqllocaldb create “MyInstance”
sqllocaldb share “MyInstance” “OurInstance”
sqllocaldb start “MyInstance”

You should add users explicitly when connected to the instance as the owner, e.g.

CREATE LOGIN [Domain\User] FROM WINDOWS;
GRANT CONNECT TO [Domain\User];
– other permissions…

In general, though, the purpose of SqlLocalDB is to serve as a sandbox for an individual developer on a machine, not to serve as a development environment for multiple users. Each user should be able to create, start, administer and use his/her own LocalDB instances.

Consume Web API in a .NET C# client

Recently I have written a console client in C# to consume those web services developed in my previous post by using APS.NET Web API 2 and Microsoft Entity Framework 6.

I started with a new Console Application (called WebApiClient) in C# in Visual Studio 2013, and then installed the Microsoft ASP.NET Web API Class Libraries using NuGet. Lastly, I added Employee.cs (model class) which was used by web services as my data structure.

The following is a web client program in C# (Program.cs):

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.Http;
using System.Net.Http.Headers;

namespace WebApiClient
{
    class Program
    {
        static void Main(string[] args)
        {
            HttpClient client = new HttpClient();
            string baseUrl = "http://localhost:55142";
            client.BaseAddress = new Uri(baseUrl);
            
            // Add an Accept header for JSON format.
            client.DefaultRequestHeaders.Accept.Add(
            new MediaTypeWithQualityHeaderValue("application/json"));

            //New Employee Record URL
            int anEmpId = -1;
            string serviceUrl;


            // 1. Post a new employee
            serviceUrl="api/employee";
            Console.WriteLine("1. Add an employee by sending POST {0}/{1}  \r\n", baseUrl, serviceUrl);
            Console.WriteLine("The following new employee is added  \r\n");
            var anEmployee = new Employee() { 
                lastname = "Smith",
                firstname = "Adam",
                title = "Economist",
                titleofcourtesy = "Dr.",
                birthdate = Convert.ToDateTime("1958-12-05 "),
                hiredate = Convert.ToDateTime("1990-01-01"),
                address = "188 Bay Street",
                city = "London",
                region = "",
                postalcode = "A1B 2Z3",
                country = "UK",
                phone = "(71) 234-8228",
                mgrid = 1};
            

            HttpResponseMessage response = client.PostAsJsonAsync(serviceUrl, anEmployee).Result;
            if  (response.IsSuccessStatusCode)
            {

                // display the new employee
                Console.WriteLine("firstname={0}", anEmployee.firstname);
                Console.WriteLine("lastname={0}", anEmployee.lastname);
            }
            else
            {
                Console.WriteLine("{0} ({1})", (int)response.StatusCode, response.ReasonPhrase);
            }

            Console.WriteLine("\r\nCheck your database table. Press any key to continue...\r\n");
            Console.ReadKey();


            // 2. Get all employees.
            serviceUrl="api/employee";
            Console.WriteLine("2. Get All Employee by sending GET {0}/{1} \r\n", baseUrl, serviceUrl);

            response = client.GetAsync(serviceUrl).Result;        // Blocking call!
            if  (response.IsSuccessStatusCode)
            {
                // Parse the response body. Blocking!
                var employees = response.Content.ReadAsAsync<IEnumerable<Employee>>().Result;
                foreach (var e in employees)
                    {
                         
                        if (e.firstname.Equals("Adam") & e.lastname.Equals("Smith"))
                        { 
                            anEmpId = e.empid;
                            Console.ForegroundColor = ConsoleColor.Red;
                            Console.WriteLine("{0};\t{1};\t{2};\t{3}", e.empid, e.firstname, e.lastname, e.title);
                            Console.ForegroundColor = ConsoleColor.Yellow;
                            Console.WriteLine("\r\nThe new employee is with empid={0}\r\n", anEmpId);
                            Console.ForegroundColor = ConsoleColor.Gray;
                        }
                        else
                        {
                            Console.WriteLine("{0};\t{1};\t{2};\t{3}", e.empid, e.firstname, e.lastname, e.title);
                        }
                    }
            }
            else
            {
                    Console.WriteLine("{0} ({1})", (int)response.StatusCode, response.ReasonPhrase);
            }
            Console.WriteLine("\r\nPress any key to continue...\r\n");
            Console.ReadKey();

            // 3. Get an employee by empid
            if (anEmpId>0)
            {
                serviceUrl = "api/employee/" + anEmpId.ToString();

            }
            else
            {
                serviceUrl = "api/employee/1";
                anEmpId = 1;
            }

            Console.WriteLine("3. Get the employee with empid={0} by sending GET {1}/{2} \r\n", anEmpId, baseUrl, serviceUrl);

            response = client.GetAsync(serviceUrl).Result;        // Blocking call!
            if (response.IsSuccessStatusCode)
            {
                // Parse the response body. Blocking!
                var a_employee = response.Content.ReadAsAsync<Employee>().Result;

                Console.WriteLine("emid={0}", a_employee.empid);
                Console.WriteLine("FirstName={0}", a_employee.firstname);
                Console.WriteLine("LastName={0}", a_employee.lastname);
                Console.WriteLine("Title={0}", a_employee.title);
            }
            else
            {
                Console.WriteLine("{0} ({1})", (int)response.StatusCode, response.ReasonPhrase);
            }
            Console.WriteLine("\r\nPress any key to continue...\r\n");
            Console.ReadKey();

            // 4. Update an employee by empid
            Console.WriteLine("4. Update an employee with empid = {0} by sending PUT {1}/{2} \r\n", anEmpId, baseUrl, serviceUrl);

            response = client.GetAsync(serviceUrl).Result;        // Blocking call!
            if (response.IsSuccessStatusCode)
            {
                // Retrieve the record first
                var a_employee = response.Content.ReadAsAsync<Employee>().Result;
                Console.WriteLine("The record is retrieved before update: \r\n");
                Console.WriteLine("emid={0}", a_employee.empid);
                Console.WriteLine("FirstName={0}", a_employee.firstname);
                Console.WriteLine("LastName={0}", a_employee.lastname);
                Console.WriteLine("Title={0}", a_employee.title);

                // Update the tile field of the record
                a_employee.title = "Senior Economist";

                response = client.PutAsJsonAsync(serviceUrl, a_employee).Result;

                if (response.IsSuccessStatusCode)
                {
                    Console.WriteLine("\r\nThe record with empid={0} was updated with the following: \r\n", anEmpId);
                    Console.ForegroundColor = ConsoleColor.Yellow; 
                    Console.WriteLine("Title={0}", a_employee.title);
                    Console.ForegroundColor = ConsoleColor.Gray;
                }
                else
                {
                    Console.WriteLine("{0} ({1})", (int)response.StatusCode, response.ReasonPhrase);
                }
            }
            else
            {
                Console.WriteLine("{0} ({1})", (int)response.StatusCode, response.ReasonPhrase);
            }
            Console.WriteLine("\r\nCheck your database table. Press any key to continue...\r\n");
            Console.ReadKey();

            // 5. delete an employee added in step 1
            Console.WriteLine("4. Delete an employee with empid = {0} by sending DELETE {1}/{2} \r\n", anEmpId, baseUrl, serviceUrl);

            response = client.DeleteAsync(serviceUrl).Result;
             if (response.IsSuccessStatusCode)
             {
                 Console.ForegroundColor = ConsoleColor.Yellow;
                 Console.WriteLine("The record with empid={0} was deleted.", anEmpId);
                 Console.ForegroundColor = ConsoleColor.Gray;
             }
             else
             {
                 Console.WriteLine("{0} ({1})", (int)response.StatusCode, response.ReasonPhrase);
             }
             Console.WriteLine("\r\nCheck your database table.\r\n");
        }
    }
}

Virtualbox: How to sync time VM client in Windows

I am running a few Virtual Machines on my PC by using Oracle Virtualbox. There is always a need to sync the time on VM clients. The following commands are used in my Windows 8 VM client to sync to the time server in Canada by ‘run as Administrator’:

Microsoft Windows [Version 6.3.9600]
(c) 2013 Microsoft Corporation. All rights reserved.

C:\Windows\system32>net stop w32time
The Windows Time service is stopping.
The Windows Time service was stopped successfully.

C:\Windows\system32>w32tm /debug /disable

C:\Windows\system32>w32tm /unregister
W32Time successfully unregistered.

C:\Windows\system32>w32tm /register
W32Time successfully registered.

C:\Windows\system32>net start w32time
The Windows Time service is starting.
The Windows Time service was started successfully.

C:\Windows\system32>w32tm /config /manualpeerlist:time.nrc.ca,0x8, /syncfromflags:manual /update
The command completed successfully.

C:\Windows\system32>w32tm /resync
Sending resync command to local computer
The command completed successfully.

Using Entity Framework with ASP.NET Web API 2 to build RESTful applications

ASP.NET Web API 2 is a framework for building RESTful applications on the .NET Framework. A broad range of clients, including browsers and mobile devices, can be built to process and present the data through HTTP web services.

In this post, I will build a basic web service by using ASP.NET Web API 2 template, reversed engineer the data model from existing database table by using Entity Framework 6, and finally scaffold and code the web service controller.

ASP.NET Web API template

Create a new project EmployeeWebAPI2 by using C# ASP.NET Application and Web API template in Microsoft Visual Studio 2013.

Reversed Engineering Model From Database

Here is the database schema in Microsoft SQL Server T-SQL.

Right Click on the project in Solution Explorer, and choose ‘Entity Framework – Reversed Engineering Code First’. Then connect to the instance (local) and database (test), and generate the model from test database for table ‘HR.Employees’. For more detail, please refer to my another post.

It will create testContext.cs, Employee.cs and EmployeeMap.cs. I commented out the key and relationship self reference to simply the object class.

Build Web Service Controller

Right Click on Controllers folder, and choose ‘Add->New Scaffold Item”. Choose ‘Web API 2 Controller with read/write Access’. Type ‘EmployeeController’ as controller name.

It will generate a EmployeeController.cs with a list of GET, POST, PUT and DELETE methods. The following steps show how to complete the various web URI methods using EF 6.

1. use the model generated from EF 6.

using EmployeeWebAPI2.Models;

2. GET api/employee

        // GET api/employee
        public IEnumerable<Employee> Get()
        {
            using (testContext entities = new testContext())
            {
                return entities.Employees.ToList<Employee>();
            }
        }

3. GET api/employee/5

        // GET api/employee/5
        public Employee Get(int id)
        {
            using (testContext entities = new testContext())
            {
                return entities.Employees.SingleOrDefault<Employee>(b => b.empid == id);
            }
        }

4. POST api/employee

        // POST api/employee
        public HttpResponseMessage Post(Employee value)
        {
            try
            {
                if (ModelState.IsValid)
                {
                    using (testContext entities = new testContext())
                    {
                        entities.Employees.Add(value);
                        entities.SaveChanges();
                        return Request.CreateResponse(HttpStatusCode.OK);
                    }
                }
                else
                {
                    return Request.CreateResponse(HttpStatusCode.InternalServerError, "invalid New Value");
                }
            }
            catch (Exception ex)
            {
                return Request.CreateResponse(HttpStatusCode.InternalServerError, ex.Message);
            }
        }

5. PUT api/employee/5

        // PUT api/employee/5
        public HttpResponseMessage Put(int id, Employee value)
        {
            try
            {
                using (testContext entities = new testContext())
                {
                    Employee myEmp = entities.Employees.SingleOrDefault<Employee>(b => b.empid == id);
                    // update all the fields
                    myEmp.empid = value.empid;
                    myEmp.lastname = value.lastname;
                    myEmp.firstname = value.firstname;
                    myEmp.title = value.title;
                    myEmp.titleofcourtesy = value.titleofcourtesy;
                    myEmp.birthdate = value.birthdate;
                    myEmp.hiredate = value.hiredate;
                    myEmp.address = value.address;
                    myEmp.city = value.city;
                    myEmp.region = value.region;
                    myEmp.postalcode = value.postalcode;
                    myEmp.country = value.country;
                    myEmp.phone = value.phone;
                    myEmp.mgrid = value.mgrid;
                    // flush to disk
                    entities.SaveChanges();
                    return Request.CreateResponse(HttpStatusCode.OK);
                }
            }
            catch (Exception ex)
            {
                return Request.CreateResponse(HttpStatusCode.InternalServerError, ex.Message);
            }
        }

6. DELETE api/employee/5

        // DELETE api/employee/5
        public HttpResponseMessage Delete(int id)
        {
            try
            {
                using (testContext entities = new testContext())
                {
                    Employee myEmp = entities.Employees.SingleOrDefault<Employee>(b => b.empid == id);
                    entities.Employees.Remove(myEmp);
                    entities.SaveChanges();
                    return Request.CreateResponse(HttpStatusCode.OK);
                }
            }
            catch (Exception ex)
            {
                return Request.CreateResponse(HttpStatusCode.InternalServerError, ex.Message);
            }
        }

Here is the complete code for EmployeeController.cs.

Test the web service

Build the solution and run the web service. Point your localhost url to:

http://localhost:55142/api/employee/2

It will get the following JSON object from url for (empid=2):


{"empid":2,"lastname":"Funk","firstname":"Don","title":"Vice President, Sales","titleofcourtesy":"Dr.","birthdate":"1962-02-19T00:00:00","hiredate":"2002-08-14T00:00:00","address":"9012 W. Capital Way","city":"Tacoma","region":"WA","postalcode":"10001","country":"USA","phone":"(206) 555-0100","mgrid":1}

I also use a tool called ‘Fiddler Web Debugger’ to examine the JSON / XML response return from the web service.

In the next post, I will write a client application to consume all the URIs in the above web api services.

Using Entity Framework in an ASP.NET MVC5 Application

In my previous two posts, I built a C# console application using Entity Framework (EF) in Microsoft Visual Studio 2013, and investigated how to perform CRUD operations on EF.

Building an ASP.NET MVC5 application using EF can become a straightforward job in Visual Studio 2013. It is very similar to building a J2EE MVC application by using JPA in Netbeans 7. The steps can be summarized as three steps: 1) create a ASP.NET MVC project; 2) add M: reversed engineer an EF model(M) from database; 3) Add C with V: scaffolding MVC 5 Controller (C) with views (V) using EF.

1. Create a ASP.NET MVC Project

In Microsoft Visual Studio 2013, create a new project (Ctrl-Shift-N) called EmployeeMVC using template (Visual C#->ASP.NET Web Application) and also select a template ‘MVC‘ and add folders and core references for ‘MVC’.

What will happene?
Visual Studio will create a few folders (App_Data, App_Start, Content, Controllers, fonts, Models, Scripts, Views) and files (Global.asax, packages.config, Web.config, Project_Readme.html, Startup.cs), also download a list of js scripts in Scripts folder, create AccountViewModels.cs and IdentityModels.cs in Models folder, AccountController.cs and HomeController.cs in Controllers folder, a list of *.shtml in various view folders, site style sheets in Contents folder and a few config.cs in App_Start.

Press F5 to build and run the empty application now.

2. Add ADO.NET Entity Data Model

Following the steps to reversed engineer EF 5 model from a table in the database into ASP.NET MVC (for reversed engineer an EF 6 model class, please use Entity Framework Power Tools):

  • Right click on Models folder, and choose New Item-Add->Data->ADO.NET Entity Data Model (C#);
  • Provide a Name: EmployeeModel.edmx and Click ‘Add’;
  • Choose ‘generate from database’ and Click ‘Next’
  • Connect to a SQL instance (local), choose your database (test) and table (HR.Employee)
  • If you receive a security warning, select OK to continue running the template.
  • This will add EmployeeModel.edmx (EF 5) as a folder under Models, and also add relevant references.

    Build the solution.

    3. Generate Controller and Views

    To generate controller and views:

  • Add the new controller to the existing Controllers folder. Right-click the Controllers folder, and select Add – New Scaffolded Item; Select the MVC 5 Controller with views, using Entity Framework option. This option will generate the controller and views for updating, deleting, creating and displaying the data in your model.
  • Set the controller name to EmployeeController, select Employee (EmployeeMVC.Models) for the model class, and select the testEntities (EmployeeMVC.Models) for the context class, Click ‘Add’
  • This will create EmployeeController.cs in Controllers:

    using System;
    using System.Collections.Generic;
    using System.Data;
    using System.Data.Entity;
    using System.Linq;
    using System.Net;
    using System.Web;
    using System.Web.Mvc;
    using EmployeeMVC.Models;
    
    namespace EmployeeMVC.Controllers
    {
        public class EmployeeController : Controller
        {
            private testEntities db = new testEntities();
    
            // GET: /Employee/
            public ActionResult Index()
            {
                var employees = db.Employees.Include(e => e.Employee1);
                return View(employees.ToList());
            }
    
            // GET: /Employee/Details/5
            public ActionResult Details(int? id)
            {
                if (id == null)
                {
                    return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
                }
                Employee employee = db.Employees.Find(id);
                if (employee == null)
                {
                    return HttpNotFound();
                }
                return View(employee);
            }
    
            // GET: /Employee/Create
            public ActionResult Create()
            {
                ViewBag.mgrid = new SelectList(db.Employees, "empid", "lastname");
                return View();
            }
    
            // POST: /Employee/Create
            // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
            // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
            [HttpPost]
            [ValidateAntiForgeryToken]
            public ActionResult Create([Bind(Include="empid,lastname,firstname,title,titleofcourtesy,birthdate,hiredate,address,city,region,postalcode,country,phone,mgrid")] Employee employee)
            {
                if (ModelState.IsValid)
                {
                    db.Employees.Add(employee);
                    db.SaveChanges();
                    return RedirectToAction("Index");
                }
    
                ViewBag.mgrid = new SelectList(db.Employees, "empid", "lastname", employee.mgrid);
                return View(employee);
            }
    
            // GET: /Employee/Edit/5
            public ActionResult Edit(int? id)
            {
                if (id == null)
                {
                    return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
                }
                Employee employee = db.Employees.Find(id);
                if (employee == null)
                {
                    return HttpNotFound();
                }
                ViewBag.mgrid = new SelectList(db.Employees, "empid", "lastname", employee.mgrid);
                return View(employee);
            }
    
            // POST: /Employee/Edit/5
            // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
            // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
            [HttpPost]
            [ValidateAntiForgeryToken]
            public ActionResult Edit([Bind(Include="empid,lastname,firstname,title,titleofcourtesy,birthdate,hiredate,address,city,region,postalcode,country,phone,mgrid")] Employee employee)
            {
                if (ModelState.IsValid)
                {
                    db.Entry(employee).State = EntityState.Modified;
                    db.SaveChanges();
                    return RedirectToAction("Index");
                }
                ViewBag.mgrid = new SelectList(db.Employees, "empid", "lastname", employee.mgrid);
                return View(employee);
            }
    
            // GET: /Employee/Delete/5
            public ActionResult Delete(int? id)
            {
                if (id == null)
                {
                    return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
                }
                Employee employee = db.Employees.Find(id);
                if (employee == null)
                {
                    return HttpNotFound();
                }
                return View(employee);
            }
    
            // POST: /Employee/Delete/5
            [HttpPost, ActionName("Delete")]
            [ValidateAntiForgeryToken]
            public ActionResult DeleteConfirmed(int id)
            {
                Employee employee = db.Employees.Find(id);
                db.Employees.Remove(employee);
                db.SaveChanges();
                return RedirectToAction("Index");
            }
    
            protected override void Dispose(bool disposing)
            {
                if (disposing)
                {
                    db.Dispose();
                }
                base.Dispose(disposing);
            }
        }
    }
    
    

    It will also create a folder ‘Employee‘ in Views with a list of cshtml (Create, Delete, Details, Edit, Index)

    Build and run by pressing F5, and go to the similar link in the browser like:

    http://localhost:49481/employee

    I removed some of unwanted items in index.cshtml. My index page looked like:

    ASP.NET MVC 5 using EF

    ASP.NET MVC 5 using EF

    Summary

    Using Entity Framework, Visual Studio 2013 can easily generate a model from database, and scaffold a controller and generate all the views based on default templates and standard CRUD operations on EF.

    The advantage of this process is that the model, controller and view can be easily re-generated by repeating the above step 2 and 3 if the table structure in the underlying physical table is changed.

    The disadvantage is also obvious. Whatever customization made after the generation on (M. V. C) will have to be repeated after re-generation.

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