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 */@Configurationpublic 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": {} }}

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