springboot 自定义消息转换器（HttpMessageConverter）

分手后的思念是犯贱 2023-02-25 02:23 5阅读 0赞

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### springboot 自定义消息转换器（HttpMessageConverter） ###

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**相关类与接口**

**HttpMessageConverter**

public interface HttpMessageConverter<T> {
    
    	boolean canRead(Class<?> clazz, @Nullable MediaType mediaType);
    
    	boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType);
    
    	List<MediaType> getSupportedMediaTypes();
    
    	T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
    			throws IOException, HttpMessageNotReadableException;
    
    	void write(T t, @Nullable MediaType contentType, HttpOutputMessage outputMessage)
    			throws IOException, HttpMessageNotWritableException;
    
    }

**AbstractHttpMessageConverter**

public abstract class AbstractHttpMessageConverter<T> implements HttpMessageConverter<T> {
    
    	protected final Log logger = HttpLogging.forLogName(getClass());
    
    	private List<MediaType> supportedMediaTypes = Collections.emptyList();
    
    	@Nullable
    	private Charset defaultCharset;
    
    
    *********
    构造函数
    
    	protected AbstractHttpMessageConverter() {
    	protected AbstractHttpMessageConverter(MediaType supportedMediaType) {
    	protected AbstractHttpMessageConverter(MediaType... supportedMediaTypes) {
    	protected AbstractHttpMessageConverter(Charset defaultCharset, MediaType... supportedMediaTypes) {
    
    
    *********
    普通方法
    
    	public void setSupportedMediaTypes(List<MediaType> supportedMediaTypes) {
    	public List<MediaType> getSupportedMediaTypes() {
    
    	public void setDefaultCharset(@Nullable Charset defaultCharset) {
    	public Charset getDefaultCharset() {
    
    	protected MediaType getDefaultContentType(T t) throws IOException {
    	protected Long getContentLength(T t, @Nullable MediaType contentType) throws IOException {
    
    	protected void addDefaultHeaders(HttpHeaders headers, T t, @Nullable MediaType contentType) throws IOException {
    
    
    	public boolean canRead(Class<?> clazz, @Nullable MediaType mediaType) {
    	protected boolean canRead(@Nullable MediaType mediaType) {
    
    	public boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType) {
    	protected boolean canWrite(@Nullable MediaType mediaType) {
    
    
    	public final T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
    	public final void write(final T t, @Nullable MediaType contentType, HttpOutputMessage outputMessage)
    
    
    *********
    抽象方法
    
    	protected abstract boolean supports(Class<?> clazz);
    
    	protected abstract T readInternal(Class<? extends T> clazz, HttpInputMessage inputMessage)
    			throws IOException, HttpMessageNotReadableException;
    
    	protected abstract void writeInternal(T t, HttpOutputMessage outputMessage)
    			throws IOException, HttpMessageNotWritableException;

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**示例**

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**config 层**

**CustomHttpMessageConverter：输出json数据时，自定义输出内容**

@Component
    public class CustomHttpMessageConverter extends AbstractHttpMessageConverter<Object> {
    
        public CustomHttpMessageConverter(){
            super(StandardCharsets.UTF_8, MediaType.ALL);
        }
    
        @Override
        protected boolean supports(Class<?> clazz) {
            return true;
        }
    
        @Override
        protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
            return JSONObject.parseObject(StreamUtils.copyToString(inputMessage.getBody(),StandardCharsets.UTF_8));
        }
    
        @Override
        protected void writeInternal(Object o, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException {
            CustomObject customObject=new CustomObject();
    
            customObject.setObject(o);
            customObject.setMessage("瓜田李下");
    
            outputMessage.getBody().write(JSONObject.toJSONBytes(customObject));
        }
    }
    
    @Data
    class CustomObject{
    
        private String message;
        private Object object;
    }

**WebConfig：添加消息转换器**

@Configuration
    public class WebConfig implements WebMvcConfigurer {
    
        @Resource
        private CustomHttpMessageConverter customHttpMessageConverter;
    
        @Override
        public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
            converters.add(customHttpMessageConverter);
        }
    }

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**controller 层**

**HelloController**

@RestController
    public class HelloController {
    
        @RequestMapping("/hello")
        public String hello(){
            return "success";
        }
    }

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**使用测试**

**localhost:8080/hello**

![20200710185930672.png][]

[20200710185930672.png]: /images/20230209/a7dc8306c3244b5fb0988da8565da97a.png