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Spring @GetMapping tutorial

Spring @GetMapping tutorial shows how to use @GetMapping annotation to map HTTP GET requests onto specific handler methods.

Spring is a popular Java application framework for creating enterprise applications.

@GetMapping

@GetMapping annotation maps HTTP GET requests onto specific handler methods. It is a composed annotation that acts as a shortcut for @RequestMapping(method = RequestMethod.GET).

Spring @GetMapping example

The following application uses @GetMapping to map two request paths onto handler methods. In this example, we use annotations to set up a Spring web application.

pom.xml
src
├───main
│   ├───java
│   │   └───com
│   │       └───zetcode
│   │           ├───config
│   │           │       MyWebInitializer.java
│   │           │       WebConfig.java
│   │           └───controller
│   │                   MyController.java
│   └───resources
│           logback.xml
└───test
    └───java
        └───com
            └───zetcode
                └───controller
                        MyControllerTest.java

This is the project structure.

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
            http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.zetcode</groupId>
    <artifactId>getmapping</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
        <spring-version>5.1.3.RELEASE</spring-version>
    </properties>

    <dependencies>

        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${spring-version}</version>
        </dependency>

    </dependencies>

    <build>
        <plugins>

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>3.2.2</version>
            </plugin>

            <plugin>
                <groupId>org.eclipse.jetty</groupId>
                <artifactId>jetty-maven-plugin</artifactId>
                <version>9.4.14.v20181114</version>
            </plugin>

        </plugins>
    </build>

</project>

In the pom.xml file we have the following dependencies: logback-classic, javax.servlet-api, junit, spring-webmvc, and spring-test.

resources/logback.xml
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <logger name="org.springframework" level="ERROR"/>
    <logger name="com.zetcode" level="INFO"/>

    <appender name="consoleAppender" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <Pattern>%d{HH:mm:ss.SSS} %blue(%-5level) %magenta(%logger{36}) - %msg %n
            </Pattern>
        </encoder>
    </appender>

    <root>
        <level value="INFO" />
        <appender-ref ref="consoleAppender" />
    </root>
</configuration>

The logback.xml is a configuration file for the Logback logging library.

com/zetcode/config/MyWebInitializer.java
package com.zetcode.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

@Configuration
public class MyWebInitializer extends
        AbstractAnnotationConfigDispatcherServletInitializer {

    @Override
    protected Class<?>[] getRootConfigClasses() {
        return null;
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {

        return new Class[]{WebConfig.class};
    }

    @Override
    protected String[] getServletMappings() {

        return new String[]{"/"};
    }
}

MyWebInitializer registers the Spring DispatcherServlet, which is a front controller for a Spring web application.

@Override
protected Class<?>[] getServletConfigClasses() {

    return new Class[]{WebConfig.class};
}

The getServletConfigClasses() returns a web configuration class.

com/zetcode/config/WebConfig.java
package com.zetcode.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;

@Configuration
@EnableWebMvc
@ComponentScan(basePackages = {"com.zetcode"})
public class WebConfig {

}

The WebConfig enables Spring MVC annotations with @EnableWebMvc and configures component scanning for the com.zetcode package.

com/zetcode/controller/MyController.java
package com.zetcode.controller;

import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {

    @GetMapping(value="/", produces = MediaType.TEXT_PLAIN_VALUE)
    public String index() {

        return "This is Home page";
    }

    @GetMapping(value="/hello", produces = MediaType.TEXT_PLAIN_VALUE)
    public String sayHello() {

        return "Hello there!";
    }
}

MyController provides mappings between request paths and handler methods.

@RestController
public class MyController {

@RestController is used for creating restful controllers, which do not use a view technology. The methods typically return XML, JSON, or plain text.

@GetMapping(value="/", produces = MediaType.TEXT_PLAIN_VALUE)
public String index() {

    return "This is Home page";
}

The @GetMapping maps a / root path from a GET request to the index() method. It returns a plain text.

com/zetcode/controller/MyControllerTest.java
package com.zetcode.controller;

import org.junit.Before;
import org.junit.Test;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

public class MyControllerTest {

    private MockMvc mockMvc;

    @Before
    public void setup() {
        this.mockMvc = MockMvcBuilders.standaloneSetup(new MyController()).build();
    }

    @Test
    public void testHomePage() throws Exception {
        this.mockMvc.perform(get("/")).andExpect(status().isOk())
                .andExpect(content().string("This is Home page"));
    }

    @Test
    public void testHelloPage() throws Exception {
        this.mockMvc.perform(get("/hello")).andExpect(status().isOk())
                .andExpect(content().string("Hello there!"));
    }
}

MyControllerTest tests the two pages.

$ curl localhost:8080
This is Home page
$ curl localhost:8080/hello
Hello there!

We run the application and create two GET requests with curl tool.

In this tutorial, we have presented the @GetMapping annotation.

You might also be interested in these related tutorials: Spring @PostMapping tutorial, Spring Singleton scope bean, Spring @ComponentScan tutorial, Spring profile XML tutorial, Java tutorial, or list all Spring tutorials.