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Spring @RequestBody tutorial

Spring @RequestBody tutorial shows how to bind method parameters to request body with @RequestBody annotation.

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

Spring @RequestBody

@RequestBody annotation binds request body to method parameters. The process of serialization/deserialization is performed by HttpMessageConverter. In addition, automatic validation can be applied by annotating the argument with @Valid.

Spring @RequestBody example

The application binds request body parameters of a form POST and JSON post request to mapped method arguments.

pom.xml
src
├───main
│   ├───java
│   │   └───com
│   │       └───zetcode
│   │           ├───bean
│   │           │       User.java
│   │           ├───config
│   │           │       MyWebInitializer.java
│   │           │       WebConfig.java
│   │           └───controller
│   │                   MyController.java
│   └───resources
│           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>springrequestbodyex</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>

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.9.8</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>

We declare the necessary dependencies. The jackson-databind is needed for serialization in HttpMessageConverter. The application runs on embedded Jetty; therefore, we declare jetty-maven-plugin.

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/bean/User.java
package com.zetcode.bean;

public class User {

    private String name;
    private String occupation;

    public User() {
    }

    public User(String name, String occupation) {
        this.name = name;
        this.occupation = occupation;
    }

    public String getName() {
        return name;
    }

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

    public String getOccupation() {
        return occupation;
    }

    public void setOccupation(String occupation) {
        this.occupation = occupation;
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("User{");
        sb.append("name='").append(name).append('\'');
        sb.append(", occupation='").append(occupation).append('\'');
        sb.append('}');
        return sb.toString();
    }
}

In the example, we have User bean which has name and occupation properties.

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.

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

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

}

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 com.zetcode.bean.User;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.util.MultiValueMap;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {

    private static final Logger logger = LoggerFactory.getLogger(MyController.class);

    @ResponseStatus(value = HttpStatus.OK)
    @PostMapping(value="/vals")
    public void process(@RequestBody MultiValueMap<String, String> values) {

        logger.info("Values:{}", values);
    }

    @ResponseStatus(value = HttpStatus.OK)
    @PostMapping(value="/user", consumes = MediaType.APPLICATION_JSON_VALUE)
    public void process2(@RequestBody User user) {

        logger.info("User: {}", user);
    }
}

In MyContoller, we have two POST mappings. We use @RequestBody to bind request parameters to MultiValueMap and User bean. The bound values are shown in logs.

$ mvn jetty:run

We start the server.

$ curl -i -d "par1=val1&par2=val2" -X POST http://localhost:8080/vals

With the curl tool, we create a reqest to the first mapping. This creates a form POST data request (content-type is application/x-www-form-urlencoded).

11:57:39.049 INFO  com.zetcode.controller.MyController - Values:{par1=[val1], par2=[val2]}

We get this log.

$ curl -i -H "Content-Type: application/json"  -d "{\"name\":\"John Doe\",\"occupation\":\"gardener\"}" -X POST "http://localhost:8080/user"

We invoke the second mapping. Here we create a request with JSON data. Note that on Windows we need to escape the double quotes.

12:02:33.817 INFO  com.zetcode.controller.MyController - User: User{name='John Doe', occupation='gardener'}

This is the output in the log.

In this tutorial, we have used the @RequestBody annotation to bind request attributes to method parameters.

You might also be interested in these related tutorials: Spring @PostMapping tutorial, Java tutorial, or list all Spring tutorials.