spring boot 自定义jsckson null转换成空字符串

在spring boot中，默认配置使用jackson,对象的null值也会被解析成null输出到前台，我们需要把null转换成空字符串

自定义一个ObjectMapper

package com.kindo.config;

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;

public class KindoObjectMapper extends ObjectMapper {

    /**
    * 
    */
    private static final long serialVersionUID = 1L;

    public KindoObjectMapper() {
        super();
        // 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