Spring mvc:annotation-driven

<mvc:annotation-driven>
        <mvc:message-converters register-defaults="true">
            <!-- 将StringHttpMessageConverter的默认编码设为UTF-8 -->
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                <constructor-arg value="UTF-8"/>
            </bean>
            <!-- 将Jackson2HttpMessageConverter的默认格式化输出设为true -->
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <property name="prettyPrint" value="true"/>
            </bean>
        </mvc:message-converters>
 </mvc:annotation-driven>

如果在spring-mvc。xml文件中配置了mvc:annotation-driven 那么服务器启动的时候会创建一个

RequestMappingHandlerAdapter对象

RequestResponseBodyMethodProcessor

@Configuration
public class WebMvcConfiguration extends WebMvcConfigurationSupport {

	/**
	 * 改变ReturnValueHandlers的顺序<br>
	 * 加入自定义RequestResponseBodyMethodProcessorExt
	 * {@link ServletInvocableHandlerMethod#invokeAndHandle(org.springframework.web.context.request.ServletWebRequest, org.springframework.web.method.support.ModelAndViewContainer, Object...)
	 * 
	 * @link HandlerMethodReturnValueHandlerComposite#getReturnValueHandler(MethodParameter)}
	 */
	@SuppressWarnings("unchecked")
	public RequestMappingHandlerAdapter requestMappingHandlerAdapter() {
		RequestMappingHandlerAdapter handlerAdapter = super.requestMappingHandlerAdapter();
		//
		List<HttpMessageConverter<?>> messageConverters = new ArrayList<>();
		StringHttpMessageConverter strConverter = new StringHttpMessageConverter(Charset.forName("UTF-8"));
//		MappingJackson2HttpMessageConverter jacksonConverter = new MappingJackson2HttpMessageConverter();
//		jacksonConverter.setPrettyPrint(true);
		messageConverters.add(strConverter);
		//messageConverters.add(jacksonConverter);
		// 需要传入参数HttpMessageConverter列表
		RequestResponseBodyMethodProcessorExt processor = new RequestResponseBodyMethodProcessorExt(messageConverters);
		try {
			Method getDefaultReturnValueHandlers = handlerAdapter.getClass().getDeclaredMethod("getDefaultReturnValueHandlers");
			getDefaultReturnValueHandlers.setAccessible(true);
			List<HandlerMethodReturnValueHandler> defaultReturnValueHandlers = (List<HandlerMethodReturnValueHandler>) getDefaultReturnValueHandlers.invoke(handlerAdapter);
			defaultReturnValueHandlers.add(0, processor);
			handlerAdapter.setReturnValueHandlers(defaultReturnValueHandlers);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return handlerAdapter;
	}

}

会导致创建两个RequestMappingHandlerAdapter对象，从而使WebMvcConfigurationSupport 子类里面的设置无效