spring-boot返回数据为null时返回空字符串

在项目开发中，我们会遇到一些null值。如果不想让返回数据有null值，而是返回空字符串该怎么办捏。

So Easy！！！

我们做一下配置就好了。

1.Jackson  null值处理：spring-boot是对Jackson默认支持的，所以有了web的依赖则不需要引入依赖了。

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
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;

/**
 * 描述: 处理数据返回的null值
 * @author Administrator
 * @create 2018-10-18 14:51
 */
@Configuration
public class JacksonConfig {
    @Bean
    @Primary
    @ConditionalOnMissingBean(ObjectMapper.class)
    public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) {
        ObjectMapper objectMapper = builder.createXmlMapper(false).build();
        objectMapper.getSerializerProvider().setNullValueSerializer(new JsonSerializer