Spring mvc3 jackson输出null为空字符串问题

转载自http://my.oschina.net/blueskyer/blog?disp=2&p=2

最近做项目，和其他人商议用json通信，因为对方是php程序员，php的编码风格对于java程序员来说就是变态，有几点变态需求：

1、json requestbody 输要用单引号(jackson默认是双引号，单引号直接报错)

2、responsebody数字输出要加引号，字段名要加引号。

3、null值为空串

 

于是查阅官方文档，终于找到方法，有点小搓，直接在Converter对象上注入一个自定义类ObjectMappingCustomer：

Xml代码  

1. <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">     
2.        <property name="messageConverters">     
3.            <list>     
4.                <bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">  
5.                    <property name="supportedMediaTypes">  
6.                        <list>  
7.                            <value>text/plain;charset=UTF-8</value>  
8.                            <value>application/json;charset=UTF-8</value>  
9.                        </list>  
10.                    </property>  
11.                    <property name="objectMapper">  
12.                        <bean class="com.wuliaolll.util.ObjectMappingCustomer"></bean>  
13.                    </property>  
14.                </bean>     
15.            </list>     
16.        </property>     
17.    </bean>     

 

Java代码 

1. package com.wuliaolll.util;  
2.   
3. import java.io.IOException;  
4.   
5. import org.codehaus.jackson.JsonGenerator;  
6. import org.codehaus.jackson.JsonParser;  
7. import org.codehaus.jackson.JsonProcessingException;  
8. import org.codehaus.jackson.map.JsonSerializer;  
9. import org.codehaus.jackson.map.ObjectMapper;  
10. import org.codehaus.jackson.map.SerializerProvider;  
11.   
12. public class ObjectMappingCustomer extends ObjectMapper  
13. {  
14.   
15.     public ObjectMappingCustomer()  
16.     {  
17.         super();  
18.         // 允许单引号  
19.         this.configure(JsonParser.Feature.ALLOW_SINGLE_QUOTES, true);  
20.         // 字段和值都加引号  
21.         this.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);  
22.         // 数字也加引号  
23.         this.configure(JsonGenerator.Feature.WRITE_NUMBERS_AS_STRINGS, true);  
24.         this.configure(JsonGenerator.Feature.QUOTE_NON_NUMERIC_NUMBERS, true);  
25.         // 空值处理为空串  
26.         this.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>()  
27.         {  
28.   
29.             @Override  
30.             public void serialize(  
31.                     Object value,  
32.                     JsonGenerator jg,  
33.                     SerializerProvider sp) throws IOException, JsonProcessingException  
34.             {  
35.                 jg.writeString("");  
36.             }  
37.         });  
38.   
39.     }  
40. }