SpringBoot自定义MessageConverter与内容协商管理器contentNegotiationManager详解

public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
	this.messageConvertersProvider.ifAvailable((customConverters) -> {
		converters.addAll(customConverters.getConverters());
	});
}

package com.decade.converters;
import com.decade.pojo.Person;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import java.io.IOException;
import java.io.OutputStream;
import java.util.List;
public class DecadeConverter implements HttpMessageConverter<Person> {
	// 只考虑写出，所以这里默认写false
    @Override
    public boolean canRead(Class<?> clazz, MediaType mediaType) {
        return false;
    }
    @Override
    public boolean canWrite(Class<?> clazz, MediaType mediaType) {
        return clazz.isAssignableFrom(Person.class);
    }
    /**
     * 统计当前converter能支持哪些类型
     * @return 返回支持的媒体类型
     */
    @Override
    public List<MediaType> getSupportedMediaTypes() {
        return MediaType.parseMediaTypes("application/x-decade");
    }
	// 只考虑写出，所以这里默认写null
    @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 {
        // 自定义想要写出的数据格式
        String result = person.getName() + ";" + person.getAge() + ";" + person.getBirth();
        // 写出
        final OutputStream body = outputMessage.getBody();
        body.write(result.getBytes());
    }
}

// 会覆盖默认的MessageConverter
default void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
}
// 不会覆盖，只会在默认的MessageConverter后面追加我们自定义的
default void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
}

package com.decade.config;
import com.decade.converters.DecadeConverter;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import java.util.List;
@Configuration(proxyBeanMethods = false)
public class MyMvcConfig implements WebMvcConfigurer {
    @Bean
    public WebMvcConfigurer createConvert() {
        return new WebMvcConfigurer() {
            @Override
            public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
                converters.add(new DecadeConverter());
            }
        };
    }
}

package com.decade.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.web.accept.HeaderContentNegotiationStrategy;
import org.springframework.web.accept.ParameterContentNegotiationStrategy;
import org.springframework.web.servlet.config.annotation.ContentNegotiationConfigurer;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
@Configuration(proxyBeanMethods = false)
public class MyMvcConfig implements WebMvcConfigurer {
    @Bean
    public WebMvcConfigurer createConvert() {
        return new WebMvcConfigurer() {
            @Override
            public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
                // 设置支持的浏览器参数类型
                Map<String, MediaType> mediaTypes = new HashMap<>();
                mediaTypes.put("json", MediaType.APPLICATION_JSON);
                mediaTypes.put("xml", MediaType.APPLICATION_XML);
                mediaTypes.put("decade", MediaType.parseMediaType("application/x-decade"));
                final ParameterContentNegotiationStrategy strategy = new ParameterContentNegotiationStrategy(mediaTypes);
                // 为了继续支持请求头参数类型，还需要往里面塞请求头内容协商管理器
                final HeaderContentNegotiationStrategy headerContentNegotiationStrategy = new HeaderContentNegotiationStrategy();
                configurer.strategies(Arrays.asList(strategy, headerContentNegotiationStrategy));
            }
        };
    }
}

@GetMapping(value = "/testPerson")
@ResponseBody
public Person testPerson() {
	Person person = new Person();
	person.setName("decade");
	person.setAge(24);
	person.setBirth(new Date());
	return person;
}