发布时Spring RestTemplate消息转换器优先级

Question

What is the most convenient way to influence the priority of the message converters Spring applies when POSTing with RestTemplate ?

Use case: I want to ensure a given entity is POSTed as JSON rather than eg XML when I do restTemplate.postForEntity(url, entity, Void.class) .

Default

By default the entity is converted to XML because the MappingJackson2XmlHttpMessageConverter takes precedence over the MappingJackson2HttpMessageConverter . The default list of converters for my app appears to be (Spring scans the classpath to see what's available):

Option 1

You can configure the message converters explicitly for a given RestTemplate instance like so restTemplate.setMessageConverters(Lists.newArrayList(new MappingJackson2HttpMessageConverter())) . This is inconvenient if the instance is shared (as a Spring bean for example) as you might need converter X in one case and converter Y in a different one.

Option 2

You can set Accept and Content-Type HTTP headers explicitly in which case Spring will use a matching message converter. The downside is that you have to resort to RestTemplate.exchange instead of RestTemplate.postForEntity which means: extra code, less convenience.

HttpHeaders requestHeaders = new HttpHeaders();
requestHeaders.setContentType(MediaType.APPLICATION_JSON);
requestHeaders.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
HttpEntity requestEntity = new HttpEntity(entity, requestHeaders);
restTemplate.exchange(url, HttpMethod.POST, requestEntity, Void.class);

Option 3

This might be what I'm looking for :)

Answer 1

According to the Spring javadoc ( https://docs.spring.io/spring-framework/docs/current/javadoc-api/index.html?org/springframework/web/client/RestTemplate.html ) you can still use postForEntity,

public <T> ResponseEntity<T> postForEntity(java.lang.String url,
                                       @Nullable
                                       java.lang.Object request,
                                       java.lang.Class<T> responseType,
                                       java.util.Map<java.lang.String,?> uriVariables)
                                throws RestClientException
....

The request parameter can be a HttpEntity in order to add additional HTTP headers to the request.