groovy优势：自定义动态Bean

开发mongodb，json很方便，但有时又需要bean，为了不固定属性，需要动态的生成bean。下面两种方式都可以实现，供参考。

groovy自定义bean

Groovy中Expando类是一种动态Bean。我们可以Expando类的实例增加属性和闭包，当我们对一个简单的bean不想为其创建一个类，是非常有用的。

def user = new Expando(username: 'mrhaki')
assert 'mrhaki' == user.username

// Add an extra property.
user.email = 'email@host.com'
assert 'email@host.com' == user.email

// Assign closure as method. The closure can
// take parameters.
user.printInfo = { writer ->
    writer << "Username: $username"
    writer << ",email: $email"
}

def sw = new StringWriter()
user.printInfo(sw)
assert 'Username: mrhaki,email: email@host.com' == sw.toString()

java利用cglib实现自定义bean

Java中要实现，利用cglib也可以实现：

public class CglibBean {  
    /** * 实体Object */  
    public Object object = null;  

    /** * 属性map */  
    public BeanMap beanMap = null;  

    public CglibBean() {  
      super();  
    }  

    @SuppressWarnings("unchecked")  
    public CglibBean(Map propertyMap) {  
      this.object = generateBean(propertyMap);  
      this.beanMap = BeanMap.create(this.object);  
    }  

    /** * 给bean属性赋值 * @param property 属性名 * @param value 值 */  
    public void setValue(String property,Object value) {  
      beanMap.put(property,value);  
    }  

    /** * 通过属性名得到属性值 * @param property 属性名 * @return 值 */  
    public Object getValue(String property) {  
      return beanMap.get(property);  
    }  

    /** * 得到该实体bean对象 * @return */  
    public Object getObject() {  
      return this.object;  
    }  

    @SuppressWarnings("unchecked")  
    private Object generateBean(Map propertyMap) {  
      BeanGenerator generator = new BeanGenerator();  
      Set keySet = propertyMap.keySet();  
      for (Iterator i = keySet.iterator(); i.hasNext();) {  
       String key = (String) i.next();  
       generator.addProperty(key,(Class) propertyMap.get(key));  
      }  
      return generator.create();  
    }  
    }

测试CglibBean

import java.lang.reflect.Method;  
import java.util.HashMap;  

/** * Cglib测试类 * @author cuiran * @version 1.0 */  
public class CglibTest {  



    @SuppressWarnings("unchecked")  
    public static void main(String[] args) throws ClassNotFoundException {  

        // 设置类成员属性 
        HashMap propertyMap = new HashMap();  

        propertyMap.put("id",Class.forName("java.lang.Integer"));  

        propertyMap.put("name",Class.forName("java.lang.String"));  

        propertyMap.put("address",Class.forName("java.lang.String"));  

        // 生成动态 Bean 
        CglibBean bean = new CglibBean(propertyMap);  

        // 给 Bean 设置值 
        bean.setValue("id",new Integer(123));  

        bean.setValue("name","454");  

        bean.setValue("address","789");  

        // 从 Bean 中获取值，当然了获得值的类型是 Object 

        System.out.println(" >> id = " + bean.getValue("id"));  

        System.out.println(" >> name = " + bean.getValue("name"));  

        System.out.println(" >> address = " + bean.getValue("address"));  

        // 获得bean的实体 
        Object object = bean.getObject();  

        // 通过反射查看所有方法名 
        Class clazz = object.getClass();  
        Method[] methods = clazz.getDeclaredMethods();  
        for (int i = 0; i < methods.length; i++) {  
            System.out.println(methods[i].getName());
        }