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
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{ "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
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{ "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
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<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
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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
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{ "flag": true, "code": "10000", "msg": "成功！", "data": { "id": 32, "templateType": 1, "templateName": "", "freightName": "", "listArea": [], "templateDescEntity": {} }} |
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原文链接：https://juejin.cn/post/6989848776361902088
