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SpringBoot自定义MessageConvert详细讲解

2023-01-11 18:00

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前言

对于页面携带的请求头中的AcceptSpringBoot有对应的10种MessageConvert可以支持写出对应的媒体类型，比如application/xml、application/json……

我们还可以通过向容器放入一个WebMvcConfigurer

实现定制化SpingMVC，自定义一个MessageConvert处理特殊的协议比如application/x-person

实现多协议数据兼容。json、xml、x-person

原理

0、@ResponseBody 响应数据出去调用 RequestResponseBodyMethodProcessor 处理

1、Processor 处理方法返回值。通过 MessageConverter 处理

2、所有 MessageConverter 合起来可以支持各种媒体类型数据的操作（读、写）

3、内容协商找到最终的 messageConverter；

实现

person类

@Data
public class Person {
    public String username;
    public Integer age;
    public Pet pet;
}

pet类

@Data
public class Pet {
    public String name;
    public Integer age;
}

PersonMessageConvert


public class PersonMessageConvert implements HttpMessageConverter<Person> {
    @Override
    public boolean canRead(Class<?> clazz, MediaType mediaType) {
        return false;
    }
    @Override
    public boolean canWrite(Class<?> clazz, MediaType mediaType) {
        return clazz.isAssignableFrom(Person.class);
    }
    
    @Override
    public List<MediaType> getSupportedMediaTypes() {
        return MediaType.parseMediaTypes("application/x-person");
    }
    @Override
    public Person read(Class<? extends Person> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
        return null;
    }
    @Override
    public void write(Person person, MediaType contentType, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException {
        //自定义协会数据的写出
        String data = person.getUsername() + ";" + person.getAge() + ";" +person.getPet() + ";";
        //写出去
        OutputStream body = outputMessage.getBody();
        body.write(data.getBytes());
    }
}

方法

    @ResponseBody
    @GetMapping("/test/person")
    public Person getPeroson() {
        Person person = new Person();
        person.setUsername("张三");
        person.setAge(18);
        person.setPet(new Pet());
        return person;
    }

WebMvcConfigurer

    @Bean
    public WebMvcConfigurer webMvcConfigurer() {
        return new WebMvcConfigurer() {
            @Override
            public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
                converters.add(new PersonMessageConvert());
            }
       }
    }

测试

拓展

如何实现访问路径携带format参数指明协商协议

比如：http://localhost:8080/test/person?format=x-person

记得先开启基于参数的内容协商

spring:
mvc:
contentnegotiation:
favor-parameter: true

@Bean
    public WebMvcConfigurer webMvcConfigurer() {
        return new WebMvcConfigurer() {
            
            @Override
            public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
                Map<String, MediaType> mediaTypeMap = new HashMap<>();
                mediaTypeMap.put("json", MediaType.APPLICATION_JSON);
                mediaTypeMap.put("xml", MediaType.APPLICATION_XML);
                mediaTypeMap.put("x-person",MediaType.parseMediaType("application/x-person"));
                //指定支持解析那些参数的媒体类型
                ParameterContentNegotiationStrategy parametertrategy = new ParameterContentNegotiationStrategy(mediaTypeMap);
                HeaderContentNegotiationStrategy headerStrategy = new HeaderContentNegotiationStrategy();
                configurer.strategies(Arrays.asList(parametertrategy, headerStrategy));
            }
            @Override
            public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
                converters.add(new PersonMessageConvert());
            }
        };
    }

测试