Spring Boot Content Negotiation Quick Start Demo

2 min readApr 17, 2024

1.What is the Content Negotiation

Simply put, the service provider returns the corresponding message according to the format supported by the client. In Spring, the REST API basically returns in json format. If you need an interface that supports json and other formats, It is obviously unreasonable to develop and maintain multiple sets of codes, and Spring just provides this function, which is ContentNegotiation. In Spring, deciding whether a data is in jso or xml is as follows:

favorPathExtension suffix pattern, for example: xxx.json, xxx.xml
favorParameter format mode, for example: xxx?format=json,xxx?format=xml,
The returned value is determined by the request’s Accept

2.Code Project

Experimental goal: Automatically switch return results in different formats according to different request parameters.

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">
    <parent>
        <artifactId>springboot-demo</artifactId>
        <groupId>com.et</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
    <artifactId>ContentNegotiation</artifactId>
    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-autoconfigure</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.dataformat</groupId>
            <artifactId>jackson-dataformat-xml</artifactId>
        </dependency>
    </dependencies>
</project>

controller

package com.et.contentnegotiation.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import java.util.HashMap;
import java.util.Map;
@Controller
public class HelloWorldController {
    @RequestMapping("/hello")
    @ResponseBody
    public Map<String, Object> showHelloWorld(){
        Map<String, Object> map = new HashMap<>();
        map.put("msg", "HelloWorld");
        return map;
    }
}

DemoApplication.java

package com.et.contentnegotiation;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoApplication {
   public static void main(String[] args) {
      SpringApplication.run(DemoApplication.class, args);
   }
}

application.yaml

server:
  port: 8088
spring:
  mvc:
    contentnegotiation:
      #favor-path-extension: true  # header accept
      favor-parameter: true   # url ?format=xml or format=json
      media-types:
        json: application/json

above it’s just some key codes,for all codes,you can see it in code repository below

Code Repository

https://github.com/Harries/springboot-demo

3.Test

favorParameter type

spring.mvc.contentnegotiation.favor-parameter=true

start spring boot application

http://127.0.0.1:8088/hello?format=xml
http://127.0.0.1:8088/hello?format=json

return multi formats

According to Accept

spring.mvc.contentnegotiation.favor-path-extension=true

Set Accept in header: application/xml or application/json