Spring Restful web services CRUD example

Web service Tutorial Content:

<dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
             <version>2.4.1</version>
 </dependency>

Now change pom.xml as follows:
pom.xml

<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 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.arpit.java2blog</groupId>
  <artifactId>SpringRestfulWebServicesWithJSONExample</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>SpringRestfulWebServicesWithJSONExample Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
   <groupId>javax.servlet</groupId>
   <artifactId>javax.servlet-api</artifactId>
   <version>3.1.0</version>
  </dependency>

  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-core</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-webmvc</artifactId>
   <version>${spring.version}</version>
  </dependency>
   <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
             <version>2.4.1</version>
        </dependency>
 </dependencies>
 <build>
  <finalName>SpringRestfulWebServicesWithJSONExample</finalName>

  <plugins>
   <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.1</version>
    <configuration>
     <source>${jdk.version}</source>
     <target>${jdk.version}</target>
    </configuration>
   </plugin>
  </plugins>

 </build>
 <properties>
  <spring.version>4.2.1.RELEASE</spring.version>
  <jdk.version>1.7</jdk.version>
 </properties>
</project>

Spring application configuration:

3) Change web.xml as below:

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>
  <servlet>
 <servlet-name>springrest</servlet-name>
 <servlet-class>
  org.springframework.web.servlet.DispatcherServlet
 </servlet-class>
 <load-on-startup>1</load-on-startup>
</servlet>

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

4) create a xml file named springrest-servlet.xml in /WEB-INF/ folder.
Please change context:component-scan if you want to use different package for spring to search for controller.Please refer to spring mvc hello world example for more understanding.

<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:context="http://www.springframework.org/schema/context"
 xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

 <mvc:annotation-driven/>
<context:component-scan base-package="org.arpit.java2blog.controller" />

</beans>

Create bean class

4) Create a bean name “Country.java” in org.arpit.java2blog.bean.

package org.arpit.java2blog.bean;

public class Country{

    int id;
    String countryName;
    long population;

    public Country() {
        super();
    }
    public Country(int i, String countryName,long population) {
        super();
        this.id = i;
        this.countryName = countryName;
        this.population=population;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getCountryName() {
        return countryName;
    }
    public void setCountryName(String countryName) {
        this.countryName = countryName;
    }
    public long getPopulation() {
        return population;
    }
    public void setPopulation(long population) {
        this.population = population;
    }

}

Create Controller

5) Create a controller named “CountryController.java” in package org.arpit.java2blog.controller

package org.arpit.java2blog.controller;

import java.util.List;
import org.arpit.java2blog.bean.Country;
import org.arpit.java2blog.service.CountryService;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class CountryController {

    CountryService countryService = new CountryService();

    @RequestMapping(value = "/countries", method = RequestMethod.GET, headers = "Accept=application/json")
    public List getCountries() {
        List listOfCountries = countryService.getAllCountries();
        return listOfCountries;
    }

    @RequestMapping(value = "/country/{id}", method = RequestMethod.GET, headers = "Accept=application/json")
    public Country getCountryById(@PathVariable int id) {
        return countryService.getCountry(id);
    }

    @RequestMapping(value = "/countries", method = RequestMethod.POST, headers = "Accept=application/json")
    public Country addCountry(@RequestBody Country country) {
        return countryService.addCountry(country);
    }

    @RequestMapping(value = "/countries", method = RequestMethod.PUT, headers = "Accept=application/json")
    public Country updateCountry(@RequestBody Country country) {
        return countryService.updateCountry(country);

    }

    @RequestMapping(value = "/country/{id}", method = RequestMethod.DELETE, headers = "Accept=application/json")
    public void deleteCountry(@PathVariable("id") int id) {
        countryService.deleteCountry(id);

    }
}

Create Service class

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.arpit.java2blog.bean.Country;

/*
 * It is just a helper class which should be replaced by database implementation.
 * It is not very well written class, it is just used for demonstration.
 */
public class CountryService {

    static HashMap<Integer,Country> countryIdMap=getCountryIdMap();

    public CountryService() {
        super();

        if(countryIdMap==null)
        {
            countryIdMap=new HashMap<Integer,Country>();
            // Creating some objects of Country while initializing
            Country indiaCountry=new Country(1, "India",10000);
            Country chinaCountry=new Country(4, "China",20000);
            Country nepalCountry=new Country(3, "Nepal",8000);
            Country bhutanCountry=new Country(2, "Bhutan",7000);

            countryIdMap.put(1,indiaCountry);
            countryIdMap.put(4,chinaCountry);
            countryIdMap.put(3,nepalCountry);
            countryIdMap.put(2,bhutanCountry);
        }
    }

    public List getAllCountries()
    {
        List countries = new ArrayList(countryIdMap.values());
        return countries;
    }

    public Country getCountry(int id)
    {
        Country country= countryIdMap.get(id);
        return country;
    }
    public Country addCountry(Country country)
    {
        country.setId(getMaxId()+1);
        countryIdMap.put(country.getId(), country);
        return country;
    }

    public Country updateCountry(Country country)
    {
        if(country.getId()<=0)
            return null;
        countryIdMap.put(country.getId(), country);
        return country;

    }
    public void deleteCountry(int id)
    {
        countryIdMap.remove(id);
    }

    public static HashMap<Integer, Country> getCountryIdMap() {
        return countryIdMap;
    }

    // Utility method to get max id
    public static int getMaxId()
    { int max=0;
    for (int id:countryIdMap.keySet()) {
        if(max<=id)
            max=id;

    }
    return max;
    }
}

7) It ‘s time to do maven build.

Right click on project -> Run as -> Maven build

Run the application

9) Right click on project -> run as -> run on server

Select apache tomcat and click on finish

10) We will test this application in  postman , UI based client for testing restful web applications. It is chrome plugin. Launch postman.If you want java based client, then you can also use how to send get or post request in java.

Get method

11) Test your get method Spring REST service
URL :“http://localhost:8080/SpringRestfulWebServicesCRUDExample/countries”.

You will get following output:

Post method

12) Post method is used to create new resource. Here we are adding new Country England to country list, so you can see we have used new country json in post body.
URL: “http://localhost:8080/SpringRestfulWebServicesCRUDExample/countries”.

Use get method to check if above country have been added to country list.

Put Method

13) Put method is used to update resource. Here will update population of nepal using put method.
We will update country json in body of request.
URL : “http://localhost:8080/SpringRestfulWebServicesCRUDExample/countries”

Use get method to check population of nepal.

Delete method

14) Delete method is used to delete resource.We will pass id of country which needs to be deleted as PathParam. We are going delete id:4 i.e. china to demonstrate delete method.

URL : “http://localhost:8080/SpringRestfulWebServicesCRUDExample/country/4”

Use get method to check country list.

As you can see, we have deleted country with id 4 i.e. china

Project structure:

We are done with Spring Restful web services json CRUD example. If you are still facing any issue, please comment.