Spring mvc3 jackson输出null为空字符串

一、使用Spring内置的支持，利用spring mvc3的注解@ResponseBody配置的json

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：

<bean class=\"org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter\">
        <property name=\"messageConverters\">
            <list>
                <bean class=\"org.springframework.http.converter.json.MappingJacksonHttpMessageConverter\">
                    <property name=\"supportedMediaTypes\">
                        <list>
                            <value>text/plain;charset=UTF-8</value>
                            <value>application/json;charset=UTF-8</value>
                        </list>
                    </property>
                    <property name=\"objectMapper\">
                        <bean class=\"com.wuliaolll.util.ObjectMappingCustomer\"></bean>
                    </property>
                </bean>
            </list>
        </property>
    </bean>

package com.wuliaolll.util;

import java.io.IOException;

import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.JsonProcessingException;
import org.codehaus.jackson.map.JsonSerializer;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializerProvider;

public class ObjectMappingCustomer extends ObjectMapper
{

    public ObjectMappingCustomer()
    {
        super();
        // 允许单引号
        this.configure(JsonParser.Feature.ALLOW_SINGLE_QUOTES, true);
        // 字段和值都加引号
        this.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
        // 数字也加引号
        this.configure(JsonGenerator.Feature.WRITE_NUMBERS_AS_STRINGS, true);
        this.configure(JsonGenerator.Feature.QUOTE_NON_NUMERIC_NUMBERS, true);
        // 空值处理为空串
        this.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>()
        {

            @Override
            public void serialize(
                    Object value,
                    JsonGenerator jg,
                    SerializerProvider sp) throws IOException, JsonProcessingException
            {
                jg.writeString("");
            }
        });

    }
}

二、json视图方式

<bean class=\"org.springframework.web.servlet.view.json.MappingJacksonJsonView\">
      <property name=\"encoding\">
          <value type=\"org.codehaus.jackson.JsonEncoding\">UTF8</value>
      </property>
      <property name=\"contentType\" value=\"application/json;charset=UTF-8\"/>
</bean>

json:
{"s":{"userId":"1","userName":"测试","passWord":"3","list":null,"dep":null,"date":1325347200000},"userForm":{"userId":"1","userName":"测试","passWord":"3","list":null,"dep":null,"date":1325347200000}}
里面有null值，怎么配置，才能让null自动变成空串

自己构建ObjectMapper注入进去，在ObjectMapper中设置NOT_NULL不转换
<bean class="org.springframework.web.servlet.view.json.MappingJacksonJsonView">
<property name="extractValueFromSingleKeyModel" value="true" />
<property name="objectMapper">
<bean class="org.codehaus.jackson.map.ObjectMapper">
<property name="serializationInclusion">
<value type="org.codehaus.jackson.map.annotate.JsonSerialize$Inclusion">NON_NULL</value>
</property>
</bean>
</property>
</bean>

参考自： />