SpringBoot 控制返回值Null转为空字符串

首先我们在网上所看到的代码，大多数长这样

package com.km66.repairshop.config;import cn.hutool.core.date.DateUtil;import com.fasterxml.jackson.core.JsonGenerator;import com.fasterxml.jackson.core.JsonParser;import com.fasterxml.jackson.core.JsonProcessingException;import com.fasterxml.jackson.databind.JsonSerializer;import com.fasterxml.jackson.databind.ObjectMapper;import com.fasterxml.jackson.databind.SerializerProvider;import com.fasterxml.jackson.databind.module.SimpleModule;import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.Primary;import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;import java.io.IOException;import java.sql.Timestamp;/**
 * @author Sir丶雨轩
 * @date 2019/3/4 15:03
 */@Configurationpublic class JacksonConfig {
    @Bean
    @Primary
    @ConditionalOnMissingBean(ObjectMapper.class)
    public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) {
        ObjectMapper objectMapper = builder.createXmlMapper(false).build();
        SerializerProvider serializerProvider = objectMapper.getSerializerProvider();
        serializerProvider.setNullValueSerializer(new JsonSerializer<Object>() {
            @Override
            public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException {
                jsonGenerator.writeString("");
            }

        });
        SimpleModule simpleModule = new SimpleModule();
        simpleModule.addSerializer(Timestamp.class, new JsonSerializer<Timestamp>() {
            @Override
            public void serialize(Timestamp value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
                gen.writeString(DateUtil.format(value,"yyyy-MM-dd HH:mm:ss"));
            }
        });
        objectMapper.registerModule(simpleModule);
        objectMapper.configure(JsonParser.Feature.ALLOW\_UNQUOTED\_CONTROL_CHARS, true) ;
        objectMapper.configure(JsonParser.Feature.ALLOW\_SINGLE\_QUOTES, true) ;
        objectMapper.configure(JsonGenerator.Feature.ESCAPE\_NON\_ASCII, true);
        return objectMapper;
    }}

其实这样没错，但是在我这里死活不好使，最终解决方案，加上如下代码

PS:在Spring Web的配置中 一般此类会实现WebMvcConfigurer接口

 @Autowired
    private ObjectMapper objectMapper;

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        converters.removeIf(item -> item instanceof FastJsonHttpMessageConverter || item instanceof MappingJackson2HttpMessageConverter);
        converters.add(new MappingJackson2HttpMessageConverter(objectMapper));
    }