Java 动态为类添加属性

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序

有一个这样的功能：展示一个报表，表头是动态的，可以手动新增或删除，也就是说会修改表结构，新增或删除表字段。然而一般实体类都是对应表结构的，那么如何给实体增加属性呢？虽然我自己的解决方案是直接返回List<map>，然后让对应的列适配到map的key中。但是这里说说给实体类动态添加属性。

实现代码

import com.google.common.collect.Maps;
import net.sf.cglib.beans.BeanGenerator;
import net.sf.cglib.beans.BeanMap;
import org.apache.commons.beanutils.PropertyUtilsBean;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;/***@author *@date 2019/10/9*@description*/
public class ReflectUtil {static Logger logger = LoggerFactory.getLogger(ReflectUtil.class);public static Object getTarget(Object dest, Map<String, Object> addProperties) {// get property mapPropertyUtilsBean 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 propertiesfor (Map.Entry<String, Object> entry : addProperties.entrySet()) {propertyMap.put(entry.getKey(), entry.getValue().getClass());}
//        addProperties.forEach((k, v) -> propertyMap.put(k, v.getClass()));// new dynamic beanDynamicBean dynamicBean = new DynamicBean(dest.getClass(), propertyMap);// add old valuefor (Map.Entry<String, Class> entry : propertyMap.entrySet()) {try {// filter extra propertiesif (!addProperties.containsKey(entry.getKey())) {dynamicBean.setValue(entry.getKey(), propertyUtilsBean.getNestedProperty(dest, entry.getKey()));}} catch (Exception e) {logger.error(e.getMessage(), e);}};// add extra valuefor (Map.Entry<String, Object> entry : addProperties.entrySet()) {try {dynamicBean.setValue(entry.getKey(), entry.getValue());} catch (Exception e) {logger.error(e.getMessage(), e);}};Object target = dynamicBean.getTarget();return target;}public static class DynamicBean {/*** 目标对象*/private Object target;/*** 属性集合*/private BeanMap beanMap;public DynamicBean(Class superclass, Map<String, Class> propertyMap) {this.target = generateBean(superclass, propertyMap);this.beanMap = BeanMap.create(this.target);}/*** bean 添加属性和值** @param property* @param value*/public void setValue(String property, Object value) {beanMap.put(property, value);}/*** 获取属性值** @param property* @return*/public Object getValue(String property) {return beanMap.get(property);}/*** 获取对象** @return*/public Object getTarget() {return this.target;}/*** 根据属性生成对象** @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();}}public static void main(String[] args) {TestClass entity = new TestClass();entity.setAge(15);entity.setId(1);entity.setName("张三");//动态设置属性字段Map<String, Object> addProperties = new HashMap() {{put("sex", "男");put("telephone", "123456789");}};//获取实体中给属性的值Object target = getTarget(entity, addProperties);System.out.println(getFieldValueByName("id", target));System.out.println(getFieldValueByName("name", target));System.out.println(getFieldValueByName("age", target));System.out.println(getFieldValueByName("sex", target));System.out.println(getFieldValueByName("telephone", target));}//获取实体中属性的值private static Object getFieldValueByName(String fieldName, Object o) {try {//通过反射获取值String firstLetter = fieldName.substring(0, 1).toUpperCase();String getter = "get" + firstLetter + fieldName.substring(1);Method method = o.getClass().getMethod(getter, new Class[]{});Object value = method.invoke(o, new Object[]{});return value;} catch (Exception e) {logger.error(e.getMessage(), e);return null;}}//测试类public static class TestClass{//IDprivate int id;//名字private String name;//年龄private int age;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}}

结果：

本文参考至：JAVA“动态”为类添加属性