动态地给Java对象添加字段并赋值

需要引入的maven依赖：

        <!--===========bean 动态 添加 字段==================-->
        <!--（必须显式添加）-->
        <dependency>
            <groupId>commons-beanutils</groupId>
            <artifactId>commons-beanutils</artifactId>
            <version>1.9.3</version>
        </dependency>
        <!--（用spring的间接依赖也可以，不必显式添加）-->
        <!--        <dependency>-->
        <!--            <groupId>cglib</groupId>-->
        <!--            <artifactId>cglib-nodep</artifactId>-->
        <!--            <version>3.2.4</version>-->
        <!--        </dependency>-->
        <!--===========bean 动态 添加 字段==================-->

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- 使用bootstrap需要导入 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-context</artifactId>
        </dependency>

        <!-- lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
        </dependency>

工具类：

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.beanutils.PropertyUtilsBean;
import org.springframework.cglib.beans.BeanGenerator;
import org.springframework.cglib.beans.BeanMap;

import java.beans.PropertyDescriptor;
import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;

/**
 *
 * 参考链接 https://www.cnblogs.com/JaxYoun/p/13923703.html
 *
 * @author: Murphy
 * @date: 2020-12-29
 */
@Slf4j
public class PropertyAppender {

    private static final class DynamicBean {

        private Object target;

        private BeanMap beanMap;

        private DynamicBean(Class superclass, Map<String, Class> propertyMap) {
            this.target = generateBean(superclass, propertyMap);
            this.beanMap = BeanMap.create(this.target);
        }

        private void setValue(String property, Object value) {
            beanMap.put(property, value);
        }

        private Object getValue(String property) {
            return beanMap.get(property);
        }

        private Object getTarget() {
            return this.target;
        }

        /**
         * 根据属性生成对象
         */
        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 Object generate(Object dest, Map<String, Object> newValueMap) throws InvocationTargetException, IllegalAccessException {
        PropertyUtilsBean propertyUtilsBean = new PropertyUtilsBean();

        //1.获取原对象的字段数组
        PropertyDescriptor[] descriptorArr = propertyUtilsBean.getPropertyDescriptors(dest);

        //2.遍历原对象的字段数组，并将其封装到Map
        Map<String, Class> oldKeyMap = new HashMap<>(4);
        for (PropertyDescriptor it : descriptorArr) {
            if (!"class".equalsIgnoreCase(it.getName())) {
                oldKeyMap.put(it.getName(), it.getPropertyType());
                newValueMap.put(it.getName(), it.getReadMethod().invoke(dest));
            }
        }

        //3.将扩展字段Map合并到原字段Map中
        newValueMap.forEach((k, v) -> oldKeyMap.put(k, v.getClass()));

        //4.根据新的字段组合生成子类对象
        DynamicBean dynamicBean = new DynamicBean(dest.getClass(), oldKeyMap);

        //5.放回合并后的属性集合
        newValueMap.forEach((k, v) -> {
            try {
                dynamicBean.setValue(k, v);
            } catch (Exception e) {
                log.error("动态添加字段【值】出错", e);
            }
        });
        return dynamicBean.getTarget();
    }

}

测试类：

import com.alibaba.fastjson.JSON;
import com.murphy.ybrain.entity.User;
import com.murphy.ybrain.utils.PropertyAppender;

import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;

/**
 * @author: Murphy
 * @date: 2020-12-29
 */
public class BeanAutoAddField {

    public static void main(String[] args) throws  InvocationTargetException, IllegalAccessException {

        User user = new User();
        user.setName("Murphy");

        System.out.println(JSON.toJSONString(user));

        System.out.println("=====================================");

        Map<String, Object> propertiesMap = new HashMap<>(2);
        propertiesMap.put("age", 18);
        propertiesMap.put("sex", "男");

        Object obj = PropertyAppender.generate(user, propertiesMap);
        System.out.println(JSON.toJSONString(obj));
    }

}

本文参考 https://www.cnblogs.com/JaxYoun/p/13923703.html