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Spring @RequestMapping tutorial

Spring @RequestMapping tutorial shows how to use @RequestMapping annotation in a Spring web application. The annotation is used for mapping web requests onto handler methods in request-handling classes.

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

@RequestMapping

@RequestMapping is used for mapping web requests onto handler methods in request-handling classes. The process of mapping web requests to handler methods is also called routing.

@RequestMapping has the following specializations:

The annotation can be used both at the class and at the method level. If used on both levels, the request paths are combined.

Spring @RequestMapping example

In the following example, we demonstrate the usage of the @RequestMapping annotation.

pom.xml
src
├───main
│   ├───java
│   │   └───com
│   │       └───zetcode
│   │           ├───config
│   │           │       MyWebInitializer.java
│   │           │       WebConfig.java
│   │           └───controller
│   │                   MyController.java
│   │                   TestController.java
│   └───resources
│           index.html
│           logback.xml
└───test
    └───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>RequestMappingEx</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>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.1.3.RELEASE</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 we have the project dependencies.

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>

This is the logback.xml configuration

resources/index.html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Home page</title>
</head>
<body>

<p>
    This is home page.
</p>

</body>
</html>

This is a home page.

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

import org.springframework.context.annotation.Configuration;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.servlet.DispatcherServlet;
import org.springframework.web.servlet.FrameworkServlet;
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 initializes the Spring web application. It contains one configuration class: WebConfig.

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.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

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

    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }
}

The WebConfig configures the Spring web application.

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

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import java.time.LocalTime;

@RestController
public class MyController {

    @RequestMapping(value = "/")
    public String home() {

        return "This is Home page";
    }

    @RequestMapping(value = "/about", method = RequestMethod.POST)
    public String about() {

        return "This is About page; POST request";
    }

    @RequestMapping(value = "/fresh", method = {RequestMethod.POST, RequestMethod.GET})
    public String fresh() {

        return "This is Fresh page; GET/POST request";
    }

    @RequestMapping(value = "/todo", consumes = "text/plain")
    public String todo() {

        return "This is Todo page; text/plain content type";
    }

    @RequestMapping(value = "/time", params = { "info=time" })
    public String showTime() {

        var now = LocalTime.now();

        return String.format("%s", now.toString());
    }
}

MyController various route definitions with @RequestMapping.

@RequestMapping(value = "/")
public String home() {

    return "This is Home page";
}

With value option, we map the / request path to the home() handler method. If not expplicitly specified, the default request method is GET. The value is an alias to the path option.

@RequestMapping(value = "/about", method = RequestMethod.POST)
public String about() {

    return "This is About page; POST request";
}

With the method option, we can narrow the handler mapping to POST requests having the /about path.

@RequestMapping(value = "/fresh", method = {RequestMethod.POST, RequestMethod.GET})
public String fresh() {

    return "This is Fresh page; GET/POST request";
}

This method can accept both GET and POST requests.

@RequestMapping(value = "/todo", consumes = "text/plain")
public String todo() {

    return "This is Todo page; text/plain content type";
}

With the consumes option we can narrow down the mapping to the requests with defined content type.

@RequestMapping(value = "/time", params = { "info=time" })
public String showTime() {

    var now = LocalTime.now();

    return String.format("%s", now.toString());
}

With the params option we narrow down the mapping to the GET requests with /time path and info=time request parameter.

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

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping(value="/test")
public class TestController {

    @RequestMapping(value = "/info")
    public String info() {

        return "This is info page";
    }

    @RequestMapping(path="*.do")
    public String somePage() {

        return "This is some page";
    }
}

TestController has additional two mappings.

@RestController
@RequestMapping(value="/test")
public class TestController {

We can place @RequestMapping on class, too. The path is then combined with the method paths.

@RequestMapping(value = "/info")
public String info() {

    return "This is info page";
}

This handler is mapped to the /test/info path.

@RequestMapping(path="*.do")
public String somePage() {

    return "This is some page";
}

The path option is equivalent to the value. It can accept Ant-style URL mappings.

$ mvn jetty:run    

We run the Jetty server.

$ curl localhost:8080
This is Home page

We generate a GET request to the home page with curl tool.

$ curl -X POST localhost:8080/about
This is About page; POST request

This is a POST request to the /about path.

$ curl -X POST localhost:8080/fresh
This is Fresh page; GET/POST request
$ curl -X GET localhost:8080/fresh
This is Fresh page; GET/POST request

The /fresh page accepts both GET and POST requests.

$ curl -d "info=time" localhost:8080/time
13:24:29.934670700

We send a request with a parameter to the /time page.

$ curl localhost:8080/test/info
This is info page

The class-level and method-level annotations are combined into the /test/info path.

$ curl localhost:8080/test/produce.do
This is some page

Finally, the ant-style mapping.

In this tutorial, we have created created various routes with @RequestMapping annotation.

You might also be interested in these related tutorials: Spring WebJars tutorial, Spring @GetMapping tutorial, Spring DefaultServlet tutorial, Introduction to Spring web applications, and Java tutorial.