SpringMVC统一转换null值为空字符串的方法

在SpringMVC中，可以通过在中配置，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() {               @Override               public  void  serialize(Object value, JsonGenerator jg, SerializerProvider sp)  throws  IOException, JsonProcessingException {                   jg.writeString( "" );               }           });       }  }
            @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

        class = "org.springframework.http.converter.json.MappingJackson2HttpMessageConverter" >
            "objectMapper" >
                class = "com.xjj.anes.mvc.converter.JsonObjectMapper" >