SpringMVC统一转换null值为空字符串的方法

在SpringMVC中，可以通过在<mvc:annotation-driven>中配置<mvc:message-converters>，把null值统一转换为空字符串，解决这个问题。下面以JSon交互的方式为例说明如何实现：

第一步：创建一个ObjectMapper

package com.xjj.anes.mvc.converter;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonGenerator;

import com.fasterxml.jackson.core.JsonProcessingException;

import com.fasterxml.jackson.databind.JsonSerializer;

import com.fasterxml.jackson.databind.ObjectMapper;

import com.fasterxml.jackson.databind.SerializerProvider;

/**

 * @description: 转换null对象为空字符串

 */

public class JsonObjectMapper extends ObjectMapper {

    private static final long serialVersionUID = 1L;

    public JsonObjectMapper() {

        super();

        // 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("");

            }

        });

    }

}

　　第二步：在SpringMVC配置文件中，把新建的ObjectMapper注入给MappingJackson2HttpMessageConverter

<!-- 注册RequestMappingHandlerMapping 和RequestMappingHandlerAdapter 两个bean。-->

<mvc:annotation-driven>

    <mvc:message-converters>

        <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">

            <property name="objectMapper">

                <bean class="com.xjj.anes.mvc.converter.JsonObjectMapper"></bean>

            </property>

        </bean>

    </mvc:message-converters>

</mvc:annotation-driven>