Spring Boot Rest API with ManyToMany Relationship

In this Post I am showing you how you can easily create Rest API using Hibernate and Spring Boot with ManyToMany Relationships between two Entities.

you can download source code at the end.

Project Structure

Calling Response from Postman tool

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Sample Json to Insert Data in Employee and Projects Table by POST  request

localhost:9090/Project

{

        "projectName": "CRISA",

        "employee" : [

{ 

        "employeeName" : "Chetan Shishodia"

            },

            { 

        "employeeName" : "Ajay Kumar"

            }

        ]

     }

        localhost:9090/Employee

{

        "employeeName": "Chetan Shishodia",

        

          "projects" : [

        { 

        "projectName" : "CRISA"

            },

            { 

        "projectName" : "FOIS"

            }

        ]

     }

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EmployeeController.java

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;
import com.restapi.entities.Employee;
import com.restapi.services.EmployeeService;

@RestController
public class EmployeeController {
 
@Autowired
EmployeeService empService;

@GetMapping("/home")
public String home() {
return "Welcome in RestApi with ManyToMany Relation home Page";
}

@GetMapping("/Employee")
public List <Employee> getEmp() {
return this.empService.getEmployees();
}

@GetMapping("/Employee/{eid}")
public Employee getEmpById(@PathVariable("eid") Integer eid) {
return this.empService.getEmployee(eid);
}

@PostMapping("/Employee" )
public Employee addEmp(@RequestBody  Employee employee) {
return this.empService.addEmployee(employee);
}

@PutMapping("/Employee")
public Employee updateEmp(@RequestBody  Employee employee) {
return this.empService.updateEmployee(employee);
}

@DeleteMapping("/Employee/{eid}")
public Integer deleteEmp(@PathVariable("eid") Integer eid) {
return this.empService.deleteEmployee(eid);
}
}

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ProjectControllers.java

package com.restapi.controllers;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

import com.restapi.entities.Projects;
import com.restapi.services.ProjectService;

@RestController
public class ProjectControllers{

@Autowired
ProjectService projectService;

@GetMapping("/Project")
public List <Projects> getProjects() {
return this.projectService.getProjects();
}

@GetMapping("/Project/{pid}")
public Projects getProject(@PathVariable("pid") Integer pid) {
return this.projectService.getProject(pid);
}

@PostMapping("/Project")
public Projects addProjects(@RequestBody  Projects project) {
return this.projectService.addProject(project);
}

@PutMapping("/Project")
public Projects updateProject(@RequestBody  Projects project) {
return this.projectService.updateProject(project);
}

@DeleteMapping("/Project/{pid}")
public Integer deleteProject(@PathVariable("pid") Integer pid) {
return this.projectService.deleteProjects(pid);
}

}

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EmployeeDao.java

package com.restapi.dao;

import org.springframework.data.jpa.repository.JpaRepository;

import com.restapi.entities.Employee;

public interface EmployeeDao extends JpaRepository<Employee, Integer>{

}

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ProjectDao.java

package com.restapi.dao;

import org.springframework.data.jpa.repository.JpaRepository;

import com.restapi.entities.Projects;

public interface ProjectDao extends JpaRepository<Projects, Integer>{

}

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Employee.java

package com.restapi.entities;

import java.io.Serializable;
import java.util.List;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
@Entity(name="Employee")
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
public class Employee implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer eid;
private String employeeName;

@ManyToMany(fetch = FetchType.LAZY,cascade = CascadeType.ALL)
@JoinTable(name="EmployeeProjectsJoin",
joinColumns = {@JoinColumn(name="eid")},
inverseJoinColumns={@JoinColumn(name="pid")})

@JsonIgnoreProperties("employee")
private List<Projects> projects;

public Integer getEid() {
return eid;
}
public void setEid(Integer eid) {
this.eid = eid;
}

public String getEmployeeName() {
return employeeName;
}
public void setEmployeeName(String employeeName) {
this.employeeName = employeeName;
}

public List<Projects> getProjects() {
return projects;
}
public void setProjects(List<Projects> projects) {
this.projects = projects;
}
public Employee(Integer eid, String employeeName, List<Projects> projects) {
super();
this.eid = eid;
this.employeeName = employeeName;
this.projects = projects;
}

public Employee() {
super();
}

}

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Projects.java

package com.restapi.entities;

import java.io.Serializable;
import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToMany;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@Entity(name="Projects")
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
public class Projects implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer pid;
private String projectName;

@ManyToMany(mappedBy="projects",fetch = FetchType.LAZY,cascade = CascadeType.ALL)
@JsonIgnoreProperties("projects")
private List<Employee> employee;

public Integer getPid() {
return pid;
}
public void setPid(Integer pid) {
this.pid = pid;
}

public String getProjectName() {
return projectName;
}
public void setProjectName(String projectName) {
this.projectName = projectName;
}

public List<Employee> getEmployee() {
return employee;
}
public void setEmployee(List<Employee> employee) {
this.employee = employee;
}
public Projects(Integer pid, String projectName, List<Employee> employee) {
super();
this.pid = pid;
this.projectName = projectName;
this.employee = employee;
}
public Projects() {
super();
}

}

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EmployeeImpl.java

package com.restapi.services;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.restapi.dao.EmployeeDao;
import com.restapi.entities.Employee;

@Service
public class EmployeeImpl implements EmployeeService{
    @Autowired
EmployeeDao empDao;

@Override
public List<Employee> getEmployees() {
// TODO Auto-generated method stub
return empDao.findAll();
}

@Override
public Employee getEmployee(Integer empId) {
// TODO Auto-generated method stub
return empDao.getOne(empId);
}

@Override
public Employee addEmployee(Employee employee) {
empDao.save(employee);
return employee;
}

@Override
public Employee updateEmployee(Employee employee) {
empDao.save(employee);
return employee;
}

@Override
public Integer deleteEmployee(Integer empId) {
int status =0;
try {
Employee emp = empDao.getOne(empId);
empDao.delete(emp);
status=1;
}catch(Exception ex) {
status=0;
ex.printStackTrace();
return status;
}
return status;
}

}

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EmployeeService.java

package com.restapi.services;
import java.util.List;

import com.restapi.entities.Employee;

public interface EmployeeService {
public List<Employee> getEmployees();
public Employee getEmployee(Integer empId);
public Employee addEmployee(Employee  emp);
public Employee updateEmployee(Employee emp);
public Integer deleteEmployee(Integer empId);
}

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ProjectImpl.java

package com.restapi.services;

import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.restapi.dao.ProjectDao;
import com.restapi.entities.Projects;

@Service
public class ProjectImpl implements ProjectService {

@Autowired
ProjectDao projectDao;

@Override
public List<Projects> getProjects() {
// TODO Auto-generated method stub
return projectDao.findAll();
}

@Override
public Projects getProject(Integer projectId) {
// TODO Auto-generated method stub
return projectDao.getOne(projectId);
}

@Override
public Projects addProject(Projects project) {
// TODO Auto-generated method stub
projectDao.save(project);
return project;
}

@Override
public Projects updateProject(Projects project) {
// TODO Auto-generated method stub
projectDao.save(project);
return project;
}

@Override
public Integer deleteProjects(Integer projectId) {
int status =0;
try {
Projects project = projectDao.getOne(projectId);
projectDao.delete(project);
   status=1;
}catch(Exception ex) {
status=0;
ex.printStackTrace();
return status;
}
return status;
}

}

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ProjectService.java

package com.restapi.services;

import java.util.List;
import com.restapi.entities.Projects;

public interface ProjectService {

public List<Projects> getProjects();
public Projects getProject(Integer projectId);
public Projects addProject(Projects  project);
public Projects updateProject(Projects project);
public Integer deleteProjects(Integer projectId);
}

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application.properties

# Changing the server port 
server.port=9090
# Database Configuration : Mysql
spring.datasource.url=jdbc:mysql://localhost/Test
spring.datasource.username=root
spring.datasource.password=admin123
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL57Dialect
spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=update
spring.jackson.serialization.fail-on-empty-beans=false

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pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.3.4.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.restAPI</groupId>
<artifactId>REST</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>RestAPI</name>
<description>RestAPI Spring Boot</description>

<properties>
<java.version>11</java.version>
</properties>

<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>

<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>

<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>

</project>

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Download Code

Functional Interfaces in java 8

A functional interface is an interface that contains only one abstract method. 

Along with the one abstract method, they can have any number of default and static methods.

In Java 8 there are four types of Functional Interfaces.

1) Predicate
2) Consumer
3) Function
4) Supplier

----------------------------------------------------------
1) Predicate gives only boolean value on the basis of one argument,
   it has only one method called test().
   
   class PredicateExample {

    public static void main(String[] args) {

    Predicate<String> checkLength = t->t.length()>3;
    System.out.println(checkLength.test("Aman"));

     }

  }
   
   // Result will be : true
   
-----------------------------------------------------------

2) Consumer only Consumes data and no output will be send.
   It has only one method called accept().
   
   class Employees{

        String name;

        public String getName() {
           return name;
        }
        public void setName(String name) {
            this.name = name;
        }
   }

  public class ConsumerExample {

    public static void main(String[] args) {

        Employees e =new Employees();
        Consumer<Employees> getNames = t->t.setName("Ajay Kumar Dargan");
        getNames.accept(e);
        System.out.println(e.getName());

     }

  }
 
  // Result will be : Ajay Kumar Dargan
 
------------------------------------------------------------

3) Function it has two arguments like Function(T , R)
   'T' represent as input and 'R' represent as output.
    It has only one method called apply().


public class FunctionExample {

     public static void main(String[] args) {

     Function<Integer,String> multiply = m->m*10+" << Multiply by 10";
        System.out.println(multiply.apply(20));

  }

}

//Result : 200 << Multiply by 10
--------------------------------------------------------------  
 
  4) Supplier does not take any arguments, but it only gives output.
     It has only one method called get().

    public class SupplierExample {

      public static void main(String[] args) {

      Supplier<Double> getRendumNum = ()->Math.random();
      System.out.println(getRendumNum.get());
    }

  }

Result : 0.1384031347391398
----------------------------------------------------------------
 

import javax.servlet.*; import java.io.IOException; import javax.servlet.http.HttpServletResponse; import org.springframework.stereotype.Component; @Component public class CORSFilter implements Filter { public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { HttpServletResponse response = (HttpServletResponse) res; // response.setHeader("Access-Control-Allow-Origin", "*"); response.setHeader("Access-Control-Allow-Methods", "POST, GET"); response.setHeader("Access-Control-Max-Age", "3700"); //response.setHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept"); chain.doFilter(req, res); } public void init(FilterConfig filterConfig) {} public void destroy() {} }

JSP Servlet Mysql CRUD Application

Project Structure

Create ActionHelper

package com.ramsis;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;



public class ActionHelper
{
public boolean addEmployee(Employee objEmployee) throws Exception{
Connection con = null;
ResultSet rs = null;
Statement stmt = null;
StringBuffer sbfQuery = null;
try
{
con = DBConnection.getConnect();
con.setAutoCommit(false);
stmt = con.createStatement();
sbfQuery = new StringBuffer();

sbfQuery.append("SELECT COUNT(*) FROM EMP ");
sbfQuery.append("WHERE emp_id = '"+objEmployee.getEmpId()+"'");
rs = stmt.executeQuery(sbfQuery.toString());
rs.next();
if(rs.getInt(1) > 0){
return false;
}

sbfQuery = new StringBuffer();
sbfQuery.append("INSERT INTO EMP(emp_id, name, design, salary)");
sbfQuery.append("VALUES('");
sbfQuery.append(objEmployee.getEmpId()+"','");
sbfQuery.append(objEmployee.getName()+"','");
sbfQuery.append(objEmployee.getDesign()+"','");
sbfQuery.append(objEmployee.getSalary()+"' )");

int iRowCount = stmt.executeUpdate(sbfQuery.toString());

if(iRowCount != 1){
return false;
}
con.commit();
}catch(Exception ex){
throw ex;
}finally{
DBConnection.closeResources(con,rs,stmt,null);
}
return true;
}



public ArrayList<Employee> getAllEmployees() throws Exception{
ArrayList<Employee> aEmployeeList = null;
Connection con = null;
ResultSet rs = null;
Statement stmt = null;
StringBuffer sbfQuery = null;
Employee objEmployee = null;
try
{
con = DBConnection.getConnect();
stmt = con.createStatement();
aEmployeeList = new ArrayList();
sbfQuery = new StringBuffer();
sbfQuery.append("SELECT * FROM EMP");
rs = stmt.executeQuery(sbfQuery.toString());

while(rs.next())
{
objEmployee = new Employee();
objEmployee.setEmpID(rs.getInt("emp_id"));
objEmployee.setName(rs.getString("name"));
objEmployee.setDesign(rs.getString("design"));
objEmployee.setSalary(rs.getInt("salary"));
aEmployeeList.add(objEmployee);
}

}catch(Exception ex){
throw ex;
}finally{
DBConnection.closeResources(con,rs,stmt,null);
}
return aEmployeeList;
}


//Method for deleting a selected employee
public boolean deleteEmployee(int iEmpID) throws Exception{
Connection con = null;
ResultSet rs = null;
Statement stmt = null;
StringBuffer sbfQuery = null;
try
{
con = DBConnection.getConnect();
stmt = con.createStatement();
sbfQuery = new StringBuffer();

con.setAutoCommit(false);

sbfQuery.append("DELETE FROM EMP WHERE emp_id = " + iEmpID);

int iRowCount = stmt.executeUpdate(sbfQuery.toString());

if(iRowCount != 1){
return false;
}
con.commit();
}catch(Exception ex){
throw ex;
}finally{
DBConnection.closeResources(con,rs,stmt,null);
}
return true;
}


}//end of class

-------------------------------------------------------------------------------------

Create ActionServlet

package com.ramsis;

import java.io.IOException;

import java.util.ArrayList;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ActionServlet extends HttpServlet
{
public void doGet(HttpServletRequest req,HttpServletResponse res)
throws ServletException,IOException
{    
processsRequest(req,res);
}

public void doPost(HttpServletRequest req,HttpServletResponse res)
throws ServletException,IOException
{
processsRequest(req,res);
}

public void processsRequest(HttpServletRequest req,HttpServletResponse res)
throws ServletException,IOException
{    
String action = null;
int iAction = 0;
ActionHelper objActionHelper= null;
Employee objEmployee = null;
ArrayList aEmployeeList = null;
String sForwardJSP = null;


try
{
action = req.getParameter("action");
objActionHelper =  new ActionHelper();
if(action != null && action.trim().length() > 0){
iAction = Integer.parseInt(action);
}

switch(iAction)
{

case 1 : // ADD_EMPLOYEE :
sForwardJSP = "/jsp/addEmployees.jsp";
break;

case 2 : // SAVE_EMPLOYEE :

objEmployee = new Employee();

objEmployee.setEmpID(Integer.parseInt(req.getParameter("emp_id").trim()));
objEmployee.setName(req.getParameter("name"));
objEmployee.setDesign(req.getParameter("design"));
objEmployee.setSalary(Integer.parseInt(req.getParameter("salary")));

if(!objActionHelper.addEmployee(objEmployee)){
req.setAttribute("Message","This Emp ID already exists.");
sForwardJSP = "/jsp/addEmployees.jsp";
}
else
{
req.setAttribute("Message","Employee is added successfully.");

aEmployeeList = objActionHelper.getAllEmployees();
req.setAttribute("EmployeeList",aEmployeeList);


sForwardJSP = "/jsp/displayEmployees.jsp";
}
break;

case 3 : // Delete an employee

String sEmpID = req.getParameter("empID");
int iEmpID = Integer.parseInt(sEmpID);

if(objActionHelper.deleteEmployee(iEmpID)){
req.setAttribute("Message","Employee is deleted successfully.");
}else{
req.setAttribute("Message","No employee matches search criteria");
}

case 4 : // get all employees

aEmployeeList = objActionHelper.getAllEmployees();
if(aEmployeeList != null && aEmployeeList.size() > 0){
req.setAttribute("EmployeeList",aEmployeeList);
}else{
req.setAttribute("Message","No employees in the system");
}
sForwardJSP = "/jsp/displayEmployees.jsp";
break;


}// end of switch

}
catch(Exception ex)
{
ex.printStackTrace();
req.setAttribute("Message",ex);
sForwardJSP = "/jsp/error.jsp";
}

// getServletConfig().getServletContext().getRequestDispatcher(sForwardJSP).forward(req,res);
RequestDispatcher dispatcher = req.getRequestDispatcher(sForwardJSP);
dispatcher.forward(req,res);


}// end of processRequest


}//end of class

-------------------------------------------------------------------------------------

Create DBConnection

package com.ramsis;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.sql.DataSource;

public class DBConnection
{
public static Connection getConnect() {

Connection con = null;

try {
   Class.forName("com.mysql.cj.jdbc.Driver");
con=DriverManager.getConnection("jdbc:mysql://localhost:3306/test?user=root&password=admin123");

            InitialContext initialContext = new InitialContext();
            Context context = (Context) initialContext.lookup("java:comp/env");
            DataSource ds = (DataSource) context.lookup("test");
            con = ds.getConnection();
} catch(Exception e) {
e.printStackTrace();
}
return con;
}

public static void closeResources(Connection con,ResultSet rs, Statement stmt, PreparedStatement p_stmt) {
try {
if(rs != null){ rs.close(); }
if(p_stmt!=null){ p_stmt.close();}
if(stmt != null){ stmt.close(); }
if(con != null){ con.close(); }
} catch(Exception e) {
System.out.println("Exception in Finally block");
e.printStackTrace();
}
}
}

-------------------------------------------------------------------------------------

Create Employee

package com.ramsis;
public class Employee
{
private int empID = 0;
private String name = null;
private String design = null;
private int salary = 0;

public void setEmpID(int empID){
this.empID= empID;
}
public int getEmpId(){
return this.empID;
}


public void setName(String name){
this.name= name;
}
public String getName(){
return this.name;
}

public void setDesign(String design){
this.design= design;
}
public String getDesign(){
return this.design;
}

public void setSalary(int salary){
this.salary= salary;
}
public int getSalary(){
return this.salary;
}

}//end of class

------------------------------------------------------------------------------------

Create addEmployees.jsp

<%
String sMessage = (String)request.getAttribute("Message");
%>


<html><head><title> Add Employee</title>
<link rel="stylesheet" href="style.css" media="screen" type="text/css">

<script>
function validate()
{
if (document.employeeform.emp_id.value=="")
{
alert("Please enter Emp ID"); return false;
}
return true;
}

function saveEmployee()
{
if(validate())
{
 document.employeeform.action.value = 2;
 document.employeeform.submit();
}
}

function viewAll(){
document.viewAllForm.action.value=4;
document.viewAllForm.submit();
}

</script>

</head>
<body>

<form name="viewAllForm" action="/CRUDOnJspServlet/ActionServlet" method="post">
<input type="hidden" name="action">
</form>


<form name="employeeform" action="/CRUDOnJspServlet/ActionServlet" method="post">
<input type="hidden" name="action">

<table border="0" align="center" cellspacing="2" cellpadding="2">

<tr><td colspan=2>
<table width="100%" border="0">
<tr><td align="left" height="40" width="30%">
<a href="javascript:viewAll()"><b>View All Emplyee</b></a>
</td></tr>
</table>
</td></tr>

<tr>
<td align="left" height="20">Emp Id</td>
<td><input type="text" name="emp_id"></td>
</tr>
<tr>
<td align="left" height="20">Name</td>
<td><input type="text" name="name"></td>
</tr>
<tr>
<td align="left" height="20">Designation</td>
<td><input type="text" name="design"></td>
</tr>
<tr>
<td align="left" height="20">Salary</td>
<td><input type="text" name="salary"></td>
</tr>

<tr>
<td align="center" colspan="2">
<input type="button" value="Add Employee" onClick="javascript:saveEmployee();"> &nbsp;&nbsp;
<input type="reset" value="Reset">
</td>
</tr>

</table>

</form>

</body>
</html>

-------------------------------------------------------------------------------------

Create displayEmployees.jsp

<%@ page import="java.util.ArrayList,com.ramsis.Employee"%>
<html>
<head>
<title> Employee Listing</title>
<link rel="stylesheet" href="style.css" media="screen" type="text/css">
</head>
<%
String sMessage = (String)request.getAttribute("Message");
Employee objEmployee = null;
ArrayList aEmployeeList = (ArrayList)request.getAttribute("EmployeeList");
%>

<script>
function addEmployee(){
document.employeeform.action.value=1;
document.employeeform.submit();
}

function deleteEmployee(empID){
if(confirm("Do you want to delete this user ? ")){
document.employeeform.empID.value  = empID;
document.employeeform.action.value = 3;
document.employeeform.submit();
}
}
</script>


<body>

<form name="employeeform" action="/CRUDOnJspServlet/ActionServlet" method="post">
<input type="hidden" name="action">
<input type="hidden" name="empID">
</form>


<table border="0" align="center" cellspacing="2" cellpadding="2" width="50%">
<tr><td colspan="2" align="left" height="20">
<%if(sMessage != null){%>
<font color="red"><%=sMessage%></font>
<%}%>
</td></tr>

<tr><td align="left">
<table width="100%" border="0">
<tr><td align="left" height="40" width="30%">
<a href="javascript:addEmployee()"><b>Add New Emplyee</b></a>
</td></tr>
</table>
<td></tr>


<%
if(aEmployeeList != null && aEmployeeList.size() > 0){
%>

<tr><td>
<!-- Employee Listing -->
<table cellspacing="0" cellpadding="2" border="1" bgcolor="lightgrey" bordercolor="blue" width="100%">
<tr>
<td align="center"><b>Emp ID</b></td>
<td align="center"><b>Name</b></td>
<td align="center"><b>Desigation</b></td>
<td align="center"><b>Salary</b></td>
<td align="center"><b>Delete</b></td>
</tr>
<%
for(int i = 0; i <aEmployeeList.size() ; i++){
objEmployee = (Employee)aEmployeeList.get(i);
%>

<tr>
<td align="center"><%=objEmployee.getEmpId()%></a></td>
<td><%=objEmployee.getName()%></td>
<td><%=objEmployee.getDesign()%></td>
<td><%=objEmployee.getSalary()%></td>
   <td align="center"><a href="javascript:deleteEmployee('<%=objEmployee.getEmpId()%>')"><p style="color:red;">Delete</p></a></td>
   
</tr>
<%
}//end of for loop
%>
</table><!- ends here -->
</td></tr>

<%
}// end of if condition
%>


</table>


</body>
</html>

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create web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" id="WebApp_ID" version="4.0">
  <display-name>CRUDOnJspServlet</display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
 
  <servlet>
<servlet-name>ActionServlet</servlet-name>
<servlet-class>com.ramsis.ActionServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>ActionServlet</servlet-name>
<url-pattern>/ActionServlet</url-pattern>
</servlet-mapping>
 
</web-app>

-------------------------------------------------------------------------------------

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How to use @Qualifier and @Primary Annotations in Spring

@Qualifier Annotation

Due to spring development there may be a situation when you create more than one bean of the same type and want to wire only one of them with a property. In such cases, you can use the @Qualifier annotation along with @Autowired to remove the confusion by specifying which exact bean will be wired.

@Primary Annotation

There may be a situation when you create more than one bean of the same type and want to wire only one of them with a property , and not want to use @Qualifier Annotation then you can Annotate any one bean as @Primary .
This annotation can be used on any class directly or indirectly annotated with the @Component annotation or on methods annotated with the @Bean annotation.

Project Code Structure

Create pom.xml file 

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">

  <modelVersion>4.0.0</modelVersion>

  <groupId>com.ramsis</groupId>

  <artifactId>springQualifierDemo</artifactId>

  <version>0.0.1-SNAPSHOT</version>

<properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

    <springframework.version>5.1.5.RELEASE</springframework.version>

    

    <maven.compiler.source>1.8</maven.compiler.source>

    <maven.compiler.target>1.8</maven.compiler.target>

  </properties>

  <dependencies>

    <dependency>

      <groupId>junit</groupId>

      <artifactId>junit</artifactId>

      <version>3.8.1</version>

      <scope>test</scope>

    </dependency>

        <dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-core</artifactId>

<version>${springframework.version}</version>

</dependency>

<!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->

<dependency>

    <groupId>org.springframework</groupId>

    <artifactId>spring-context</artifactId>

    <version>${springframework.version}</version>

</dependency>

  </dependencies>

</project>

-------------------------------------------------------------------------------------------- 

Create CompanyInfo Class

package com.ramsis.bean;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.beans.factory.annotation.Qualifier;

import org.springframework.stereotype.Component;

@Component

public class CompanyInfo {

@Autowired

@Qualifier("hyundai")

CompanyType companytype;

public void getInfo() {

companytype.getCompanyType();

}

}

--------------------------------------------------------------------------------------------

Create CompanyType Class

package com.ramsis.bean;

public interface CompanyType {

public void getCompanyType();

}

--------------------------------------------------------------------------------------------

Create Hyundai Class

package com.ramsis.bean;

import org.springframework.stereotype.Component;

@Component

public class Hyundai implements CompanyType {

@Override

public void getCompanyType() {

        System.out.println("Hyundai making Automobiles.");

}

}

--------------------------------------------------------------------------------------------

Create Nokia Class

package com.ramsis.bean;

import org.springframework.stereotype.Component;

@Component

public class Nokia implements CompanyType {

@Override

public void getCompanyType() {

  System.out.println("Nokia making Mobile Phones.");

}

}

--------------------------------------------------------------------------------------------

Create Reymond Class

package com.ramsis.bean;

import org.springframework.context.annotation.Primary;

import org.springframework.stereotype.Component;

@Component

@Primary

public class Reymond implements CompanyType {

@Override

public void getCompanyType() {

        System.out.println("Reymonds making fabrics and fashion products.");

}

}

--------------------------------------------------------------------------------------------

Create Runner Class

package com.ramsis.Main;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.ramsis.bean.CompanyInfo;

import com.ramsis.config.Config;

public class Runner {

public static void main(String args[]) {

AnnotationConfigApplicationContext  context = new      AnnotationConfigApplicationContext(Config.class);

CompanyInfo info =context.getBean("companyInfo",CompanyInfo.class);

info.getInfo();

context.close();

}

}

--------------------------------------------------------------------------------------------

Create Config Class

package com.ramsis.config;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

@Configuration
@ComponentScan(basePackages="com.ramsis.bean")
public class Config {

}

--------------------------------------------------------------------------------------------

After run this project you will get the output as below mention image

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