如何在使用RestTemplate时配置内部Jackson映射器？

Question

我想更新Spring RestTemplate使用的jackson映射器的SerializationConfig.Feature ...属性，不知道如何获取它或我可以/应该配置它。

Answer 1

默认RestTemplate构造登记了一套HttpMessageConverter S：

this.messageConverters.add(new ByteArrayHttpMessageConverter()); 
this.messageConverters.add(new StringHttpMessageConverter()); 
this.messageConverters.add(new ResourceHttpMessageConverter()); 
this.messageConverters.add(new SourceHttpMessageConverter()); 
this.messageConverters.add(new XmlAwareFormHttpMessageConverter()); 
if (jaxb2Present) { 
    this.messageConverters.add(new Jaxb2RootElementHttpMessageConverter()); 
} 
if (jacksonPresent) { 
    this.messageConverters.add(new MappingJacksonHttpMessageConverter()); 
} 
if (romePresent) { 
    this.messageConverters.add(new AtomFeedHttpMessageConverter()); 
    this.messageConverters.add(new RssChannelHttpMessageConverter()); 
} 

轮流的MappingJacksonHttpMessageConverter，直接创造ObjectMapper实例。您可以找到该转换器并替换ObjectMapper或在其之前注册一个新转换器。这应该工作：

@Bean 
public RestOperations restOperations() { 
    RestTemplate rest = new RestTemplate(); 
    //this is crucial! 
    rest.getMessageConverters().add(0, mappingJacksonHttpMessageConverter()); 
    return rest; 
} 

@Bean 
public MappingJacksonHttpMessageConverter mappingJacksonHttpMessageConverter() { 
    MappingJacksonHttpMessageConverter converter = new MappingJacksonHttpMessageConverter(); 
    converter.setObjectMapper(myObjectMapper()); 
    return converter; 
} 

@Bean 
public ObjectMapper myObjectMapper() { 
    //your custom ObjectMapper here 
} 

在XML是沿着这些路线的东西：

<bean id="restOperations" class="org.springframework.web.client.RestTemplate"> 
    <property name="messageConverters"> 
     <util:list> 
      <bean class="org.springframework.http.converter.ByteArrayHttpMessageConverter"/> 
      <bean class="org.springframework.http.converter.StringHttpMessageConverter"/> 
      <bean class="org.springframework.http.converter.ResourceHttpMessageConverter"/> 
      <bean class="org.springframework.http.converter.xml.SourceHttpMessageConverter"/> 
      <bean class="org.springframework.http.converter.xml.XmlAwareFormHttpMessageConverter"/> 
      <bean class="org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter"/> 
      <bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"> 
       <property name="objectMapper" ref="customObjectMapper"/> 
      </bean> 
     </util:list> 
    </property> 
</bean> 

<bean id="customObjectMapper" class="org.codehaus.jackson.map.ObjectMapper"/> 

注意，转变是不是真的1：1 - 我要明确地建立在XML messageConverters列表，同时用@Configuration方法我可以参考现有的并简单地修改它。但这应该工作。

Answer 2

RestTemplate将初始化其默认消息转换器。你应该用你自己的bean代替MappingJackson2HttpMessageConverter，它应该使用你想要使用的对象映射器。这为我工作：

@Bean 
public RestTemplate restTemplate() { 
    final RestTemplate restTemplate = new RestTemplate(); 

    //find and replace Jackson message converter with our own 
    for (int i = 0; i < restTemplate.getMessageConverters().size(); i++) { 
     final HttpMessageConverter<?> httpMessageConverter = restTemplate.getMessageConverters().get(i); 
     if (httpMessageConverter instanceof MappingJackson2HttpMessageConverter){ 
      restTemplate.getMessageConverters().set(i, mappingJackson2HttpMessageConverter); 
     } 
    } 

    return restTemplate; 
} 

@Bean 
public MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter() { 
    MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter(); 
    converter.setObjectMapper(myObjectMapper()); 
    return converter; 
} 

@Bean 
public ObjectMapper myObjectMapper() { 
    // return your own object mapper 
} 

Answer 3

如果不使用Spring IoC，你可以做这样的事情（的Java 8）：

ObjectMapper objectMapper = new ObjectMapper(); 
// configure your ObjectMapper here 

RestTemplate restTemplate = new RestTemplate();  

MappingJackson2HttpMessageConverter messageConverter = new MappingJackson2HttpMessageConverter(); 
messageConverter.setPrettyPrint(false); 
messageConverter.setObjectMapper(objectMapper); 
restTemplate.getMessageConverters().removeIf(m -> m.getClass().getName().equals(MappingJackson2HttpMessageConverter.class.getName())); 
restTemplate.getMessageConverters().add(messageConverter); 

Answer 4

要完成其他答案：如果你ObjectMapper只是注册了一个杰克逊Module自定义串行/解串器，您可能要对现有ObjectMapper从RestTemplate的默认MappingJackson2HttpMessageConverter直接登录你的模块如下（不包括DI的例子，但同样适用，如果使用DI）：

SimpleModule module = new SimpleModule(); 
    module.addSerializer(...); 
    module.addDeserializer(...); 

    MappingJackson2HttpMessageConverter messageConverter = restTemplate.getMessageConverters().stream() 
        .filter(MappingJackson2HttpMessageConverter.class::isInstance) 
        .map(MappingJackson2HttpMessageConverter.class::cast) 
        .findFirst().orElseThrow(() -> new RuntimeException("MappingJackson2HttpMessageConverter not found")); 
    messageConverter.getObjectMapper().registerModule(module); 

这将允许您完成原始ObjectMapper（由Spring的Jackson2ObjectMapperBuilder完成）的配置，而不是替换它。