用反射实现JavaBean和Map之间的转换

学习内容：

需求
由于JavaBean结构与Map类似，我们可以把JavaBean与Map进行转换

代码如下：

package com.yy;

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

/**
 * @author YanYang
 * @description: 采用单例模式实现
 * @date 2021/4/10 13:12
 */
public class JavaBeanChangeMap {
    private static final JavaBeanChangeMap javaBeanChangeMap = new JavaBeanChangeMap();

    private JavaBeanChangeMap() {
    }
    public static JavaBeanChangeMap getInstance() {
        return javaBeanChangeMap;
    }

    /**
     * JavaBean 转 Map
     */
    public <T> Map<String, Object> JavaBeanToMap(Class<T> t) throws IntrospectionException, InvocationTargetException, IllegalAccessException, InstantiationException, NoSuchMethodException {
        // 1、创建 Map 集合
        Map<String, Object> map = new HashMap<>();
        // 2、通过内省机制获取 PropertyDescriptors 属性数组
        // Object.class
        PropertyDescriptor[] propertyDescriptors = Introspector.getBeanInfo(Person.class, Object.class)
                .getPropertyDescriptors();

        Constructor<T> constructor = t.getConstructor(String.class, int.class);
        Object obj = constructor.newInstance("afa", 12);
        System.out.println("obj = " + obj);
        // 3、遍历该数组获取 Get 方法，获取属性名作为 key ，获取对象值作为 value
        for(PropertyDescriptor propertyDescriptor : propertyDescriptors) {
            String name = propertyDescriptor.getName();
            Method readMethod = propertyDescriptor.getReadMethod();
            Object invoke = readMethod.invoke(obj);
            map.put(name, invoke);
        }
        return map;
    }

    /**
     * Map 转 JavaBean
     */
    public <T> T mapToJavaBean(Map map, Class<T> c) throws IllegalAccessException, InstantiationException, IntrospectionException, InvocationTargetException {
        // 1、通过字节码对象创建空的实例
        T o =  c.newInstance();
        // 2、通过 Introspector 类把bean对象信息封装到 beanInfo 中
        BeanInfo beanInfo = Introspector.getBeanInfo(c, Object.class);
        // 3、通过 getPropertyDescriptors() 获取一个属性(get/set)数组
        PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();
        // 4、遍历该数组，把获取的名字作为 map 的 key，通过 key 取出对应的 value 值
        for (PropertyDescriptor propertyDescriptor : propertyDescriptors) {
            String key = propertyDescriptor.getName();
            Object value = map.get(key);
            Method writeMethod = propertyDescriptor.getWriteMethod();
            writeMethod.invoke(o, value);
        }
        return o;
    }
}

Junit测试代码：

package com.yy.test;

import com.yy.JavaBeanChangeMap;
import com.yy.Person;
import org.junit.Test;

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

/**
 * @author YanYang
 * @description: 测试
 * @date 2021/4/10 13:00
 */
public class JavaBeanChangeMapTest {
    @Test
    public void testJavaBeanToMap() throws Exception {
        Map<String, Object> map = JavaBeanChangeMap.getInstance().JavaBeanToMap(Person.class);
        System.out.println("map = " + map);
        System.out.println("================================");
    }

    @Test
    public void testMapToJavaBean() throws Exception {
        Map map = new HashMap();
        map.put("name", "afa");
        map.put("age", 12);
        Person person = JavaBeanChangeMap.getInstance().mapToJavaBean(map, Person.class);
        System.out.println("person = " + person);
    }
}

运行结果：

"C:\Program Files\Java\jdk-11.0.9\bin\java.exe"
obj = Person{name='afa', age=12}
map = {name=afa, age=12}
================================
person = Person{name='afa', age=12}

Process finished with exit code 0

总结：

反射基础去请看我的上一篇博客：上篇博客地址