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;
@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": {}
}
}
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