java為實體動態添加字段

轉載：https://www.jianshu.com/p/962bc2d2fa1b

 

 

對於線上已經在用的接口，要動態的擴展返回數據的字段，並且不同的調用商需要的字段不一樣，為了A客戶增加了一個字段，不能把字段返回給B，防止B客戶那邊也要升級接口。對於開始加一兩個字段我還可以接受：每次返回不同的實例，漸漸的我覺得力不從心了，代碼重復太多了，就想到了能不能動態的添加字段呢？
首先引入maven依賴：

作者：風一樣的存在
鏈接：https://www.jianshu.com/p/962bc2d2fa1b
來源：簡書
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        <dependency> <groupId>commons-beanutils</groupId> <artifactId>commons-beanutils</artifactId> <version>1.9.3</version> </dependency> <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-lang3</artifactId> <version>3.8</version> </dependency> <dependency> <groupId>cglib</groupId> <artifactId>cglib-nodep</artifactId> <version>3.2.4</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.16.22</version> </dependency> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.9.6</version> </dependency>

 

import com.fasterxml.jackson.databind.ObjectMapper; import com.google.common.collect.Maps; import lombok.AllArgsConstructor; import lombok.Builder; import lombok.Data; import lombok.NoArgsConstructor; import net.sf.cglib.beans.BeanGenerator; import net.sf.cglib.beans.BeanMap; import org.apache.commons.beanutils.PropertyUtilsBean; import java.beans.PropertyDescriptor; import java.util.Map; /** * @author: jack * @Date: 2019/5/15 21:30 * @Description: 動態添加類的屬性 */ public class ReflectUtil { public static Object getTarget(Object dest, Map<String, Object> addProperties) { PropertyUtilsBean propertyUtilsBean =new PropertyUtilsBean(); PropertyDescriptor[] descriptors = propertyUtilsBean.getPropertyDescriptors(dest); Map<String, Class> propertyMap = Maps.newHashMap(); for(PropertyDescriptor d : descriptors) { if(!"class".equalsIgnoreCase(d.getName())) { propertyMap.put(d.getName(), d.getPropertyType()); } } // add extra properties addProperties.forEach((k, v) -> propertyMap.put(k, v.getClass())); // new dynamic bean DynamicBean dynamicBean =new DynamicBean(dest.getClass(), propertyMap); // add old value propertyMap.forEach((k, v) -> { try{ // filter extra properties if(!addProperties.containsKey(k)) { dynamicBean.setValue(k, propertyUtilsBean.getNestedProperty(dest, k)); } }catch (Exception e) { e.printStackTrace(); } }); // add extra value addProperties.forEach((k, v) -> { try{ dynamicBean.setValue(k, v); }catch (Exception e) { e.printStackTrace(); } }); Object target = dynamicBean.getTarget(); return target; } public static class DynamicBean { /** * 目標對象 */ private Object target; /** * 屬性集合 */ private BeanMap beanMap; public DynamicBean(Class superclass, Map<String, Class> propertyMap) { this.target = generateBean(superclass, propertyMap); this.beanMap = BeanMap.create(this.target); } /** * bean 添加屬性和值 * * @param property * @param value */ public void setValue(String property, Object value) { beanMap.put(property, value); } /** * 獲取屬性值 * * @param property * @return */ public Object getValue(String property) { return beanMap.get(property); } /** * 獲取對象 * * @return */ public Object getTarget() { return this.target; } /** * 根據屬性生成對象 * * @param superclass * @param propertyMap * @return */ private Object generateBean(Class superclass, Map<String, Class> propertyMap) { BeanGenerator generator =new BeanGenerator(); if(null != superclass) { generator.setSuperclass(superclass); } BeanGenerator.addProperties(generator, propertyMap); return generator.create(); } } @Data @Builder @AllArgsConstructor @NoArgsConstructor public static class Student { private String name; private String email; } public static void main(String[] args) throws Exception{ Student student = Student.builder().name("jack").email("[e-mail]").build(); System.out.println(student.toString()); Map<String,Object> properties = Maps.newHashMap(); properties.put("address","浙江杭州"); properties.put("age",26); ObjectMapper mapper = new ObjectMapper(); String json = mapper.writeValueAsString(getTarget(student,properties)); System.out.println(json); } }