springboot配置Jackson返回统一默认值的实现示例

在项目开发中，我们返回的数据或者对象没有的时候一般直接返回的null

有数据时的返回值

{
 "flag": true,
 "code": "10000",
 "msg": "成功！",
 "data": {
  "id": 32,
  "templateType": 1,
  "templateName": "我的测试模板1",
  "freightName": "我的测试标题1",
  "listArea": [
   {
    "id": 968,
    "templateId": 32,
    "freightPrice": 15,
   }
  ],
  "templateDescEntity": {
   "id": 1
   "name": "xxx"
  }
 }
}

没有数据时的返回值

{
 "flag": true,
 "code": "10000",
 "msg": "成功！",
 "data": {
  "id": 32,
  "templateType": 1,
  "templateName": null,
  "freightName": null,
  "listArea": null,
  "templateDescEntity": null
 }
}

这种情况下数据返回给前端，前端需要做大量的空值判断
如前端调使用属性data.templateDescEntity.id的时候就会直接报异常
此时我们可以使用返回值统一处理，配置如下

pom.xml添加

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.9.5</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
</dependency>

java类添加配置

package com.ys.mall.core.product.config;

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;
import java.lang.reflect.Field;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Objects;

/**
 * 数据返回给前端时，设置null值默认为""
 *
 * @author cgh
 * @date 2020/12/14 10:35
 */
@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<Object>() {
            @Override
            public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
                String fieldName = jsonGenerator.getOutputContext().getCurrentName();
                try {
                    //反射获取字段类型
                    Field field = jsonGenerator.getCurrentValue().getClass().getDeclaredField(fieldName);
                    if (CharSequence.class.isAssignableFrom(field.getType())) {
                        //字符串型空值""
                        jsonGenerator.writeString("");
                        return;
                    } else if (Collection.class.isAssignableFrom(field.getType())) {
                        //列表型空值返回[]
                        jsonGenerator.writeStartArray();
                        jsonGenerator.writeEndArray();
                        return;
                    } else if (Map.class.isAssignableFrom(field.getType())) {
                        //map型空值 或者 bean对象 返回{}
                        jsonGenerator.writeStartObject();
                        jsonGenerator.writeEndObject();
                        return;
                    }
                } catch (NoSuchFieldException ignored) {
                }

                jsonGenerator.writeString("");
            }
        });
        return objectMapper;
    }
}

添加空值统一处理后的返回值

{
 "flag": true,
 "code": "10000",
 "msg": "成功！",
 "data": {
  "id": 32,
  "templateType": 1,
  "templateName": "",
  "freightName": "",
  "listArea": [],
  "templateDescEntity": {}
 }
}

到此这篇关于springboot配置Jackson返回统一默认值的实现示例的文章就介绍到这了,更多相关springboot Jackson返回统一默认值内容请搜索自由互联以前的文章或继续浏览下面的相关文章希望大家以后多多支持自由互联！