一个Spring + Json异常的问题

Spring可以轻易实现在Controller中将一个对象转成Json放在ResponseBody中返回，如下：

@RequestMapping(value = "/getqbankrecord/{qbId}/{id}", method = RequestMethod.GET) @ResponseBody public QuestionRecord getQuestionBankRecord(@PathVariable("qbId") int qbId, @PathVariable("id") int id, HttpServletRequest request) { assert(qbService != null); this.logger.info("this is getQuestionBankRecord ......"); QuestionRecord record = qbService.getQRecord(qbId, id); return record; }

并且在容器中配置messageConverters

<!-- Json --> 
    <beans:bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
        <beans:property name="messageConverters">
            <util:list id="beanList">
                <beans:bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
                    <!-- 
					<beans:property name="supportedMediaTypes"> 
					   <beans:list> 
					       <beans:value>text/html;charset=UTF-8</beans:value> 
					       <beans:value>text/json;charset=UTF-8</beans:value>
					       <beans:value>application/json;charset=UTF-8</beans:value>
					   </beans:list> 
					</beans:property>  
					 -->                                       
                </beans:bean>
            </util:list>
        </beans:property>
    </beans:bean>

org.springframework.web.HttpMediaTypeNotAcceptableException: Could not find acceptable representation at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter$ServletHandlerMethodInvoker.writeWithMessageConverters(AnnotationMethodHandlerAdapter.java:1050) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter$ServletHandlerMethodInvoker.handleResponseBody(AnnotationMethodHandlerAdapter.java:990) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter$ServletHandlerMethodInvoker.getModelAndView(AnnotationMethodHandlerAdapter.java:939) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:438) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:424)

TestA类非常简单，就一个List成员变量

public class TestA {
	private List<String> items;

	public TestA()
	{
		items = new ArrayList<String>();
	}
	public void add(String t)
	{
		items.add(t);
	}
}

开始总以为是Content-Type或者Accept属性有问题，但找了半天原因才发现这里有个基本的要求：POJO对象要转成Json，则要求POJO中的属性必须都有getter方法，加上getter方法后就正常了 ：）