Java異常處理008：RestTemplate請求Could not extract response: no suitable HttpMessageConverter found for response type.... content type [text/html;charset=UTF-8]異常

start

　　1-異常日誌：

2020-12-02 16:42:39.386 ERROR 6180 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.web.client.UnknownContentTypeException: Could not extract response: no suitable HttpMessageConverter found for
 
 response type [class com.tyj.study.rest_template.ResponseB] and content type [text/html;charset=UTF-8]] with root cause

org.springframework.web.client.UnknownContentTypeException: Could not extract response: no suitable HttpMessageConverter found for response type [class com.tyj.study.rest_template.ResponseB] and content type [text/html;charset=UTF-8
 
]
    at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:126) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:998) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:
 
981) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:741) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:674) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
    at org.springframework.web.client.RestTemplate.getForEntity(RestTemplate.java:342) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
......

　　2-異常原因：即RestTemplate請求不支援content type [text/html;charset=UTF-8]型別


　　3-Springboot注入RestTemplate類
　　　　追蹤RestTemplate例項化過程發現預設的RestTemplate只支援application/json格式，所以需要手動補充text/html格式

    @Bean("restTemplate")
    @Primary
    public RestTemplate restTemplate(){
        RestTemplate restTemplate = new RestTemplate();
        return restTemplate;


    }

    public RestTemplate() {
        ......
       if (jackson2Present) {
          this.messageConverters.add(new MappingJackson2HttpMessageConverter());
       }
       .....
    }

    public MappingJackson2HttpMessageConverter() {
        this(Jackson2ObjectMapperBuilder.json().build());
    }

    public MappingJackson2HttpMessageConverter(ObjectMapper objectMapper) {
        super(objectMapper, MediaType.APPLICATION_JSON, new MediaType("application", "*+json"));
    }

4-解決方案
　　支援text/plan,text/html格式

    @Bean("restTemplate")
    public RestTemplate restTemplate(){
        RestTemplate restTemplate = new RestTemplate();
        MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter = new MappingJackson2HttpMessageConverter();
        mappingJackson2HttpMessageConverter.setSupportedMediaTypes(Arrays.asList(
                MediaType.TEXT_HTML,
                MediaType.TEXT_PLAIN));
        restTemplate.getMessageConverters().add(mappingJackson2HttpMessageConverter);

        return restTemplate;
    }

end