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前言

一套系统适配多端数据返回

1、多端内容适配

基于请求头内容协商（默认开启）

客户想服务器发送请求，携带http标准的Accept请求头
Accept:application/json text/xml text/yaml
服务端根据客户端请求头期望的数据类型进行动态返回

基于请求参数内容协商（需要开启）

发送请求 Get/projects/spring-boot?format=json
匹配到@GetMapping(*/projects/spring-boot*)
根据参数协商，优先返回json类型数据（需要开启参数匹配设置）
发送请求Get/projects/spring-boot?format=xml 优先返回xml类型数据

2、默认返回json数据

 @GetMapping("/person")public Person person(){Person person = new Person();person.setId(1l);person.setUserName("张三");person.setEmail("2aaa@qq.com");person.setAge(18);return person;}

3、设置返回xml数据

导入jackson-dataformat-xml包

<dependency><groupId>com.fasterxml.jackson.dataformat</groupId><artifactId>jackson-dataformat-xml</artifactId><version>2.15.3</version></dependency>

在类文件中添加注解 @JacksonXmlRootElement

4、基于请求参数内容协商功能，默认参数是format

在配置文件中配置

5、内容协商的原理–httpMessageConverter

@ResponseBody 由HttpMessageConverter处理

6、增加yaml内容协商

导入yaml文件

把测试对象写成yaml

public static void main(String[] args) throws JsonProcessingException {Person person = new Person();person.setId(1l);person.setUserName("张三");person.setEmail("2aaa@qq.com");person.setAge(18);YAMLFactory factory = new YAMLFactory().disable(YAMLGenerator.Feature.WRITE_DOC_START_MARKER);ObjectMapper mapper = new ObjectMapper(factory);String s = mapper.writeValueAsString(person);System.out.println(s);}

在配置中增加yaml类型

#增加一种新的内容类型
spring.mvc.contentnegotiation.media-types.yaml=text/yaml

在config下配置一个把对象转为yaml的类

package com.atguigu.boot304demo.config;import com.atguigu.boot304demo.component.MyYamlHttpMessageConverter;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.CacheControl;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;import java.util.List;
import java.util.concurrent.TimeUnit;/*** @author jitwxs* @date 2023年10月20日 10:18*/
//@EnableWebMvc //禁用boot的默认设置
@Configuration //这是一个配置类,给容器中放一个WevMvcConfigurer组件,就能自定义底层
public class MyConfig {@Beanpublic WebMvcConfigurer webMvcConfigurer(){return new WebMvcConfigurer() {@Overridepublic void addResourceHandlers(ResourceHandlerRegistry registry) {registry.addResourceHandler("/static/**").addResourceLocations("classPath:/a/", "classpath:/b/").setCacheControl(CacheControl.maxAge(1180, TimeUnit.SECONDS));}@Overridepublic void extendMessageConverters(List<HttpMessageConverter<?>> converters) {converters.add(new MyYamlHttpMessageConverter());}};}
}

定义类

package com.atguigu.boot304demo.component;import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
import com.fasterxml.jackson.dataformat.yaml.YAMLGenerator;
import lombok.Data;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.AbstractHttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.ResponseBody;import java.io.IOException;
import java.io.OutputStream;
import java.nio.charset.Charset;/*** @author jitwxs* @date 2023年10月21日 12:50*/
public class MyYamlHttpMessageConverter extends AbstractHttpMessageConverter<Object> {private ObjectMapper objectMapper = null;public MyYamlHttpMessageConverter(){
//        支持哪种媒体类型super(new MediaType("text","yaml", Charset.forName("UTF-8")));YAMLFactory factory = new YAMLFactory().disable(YAMLGenerator.Feature.WRITE_DOC_START_MARKER);this.objectMapper = new ObjectMapper(factory);}@Overrideprotected boolean supports(Class<?> clazz) {
//        只要对象类型，不要基本类型return true;}@Override  //@RequestBodyprotected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {return null;}@Override  //@ResponseBody   //把对象怎样写出来protected void writeInternal(Object o, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException {
//        try-with写法,自动关流
//        try(OutputStream os = outputMessage.getBody()){
//            this.objectMapper.writeValue(os, o);
//        }OutputStream body = outputMessage.getBody();try {this.objectMapper.writeValue(body,o);}finally {body.close();}}
}

效果