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今天练习了一下动态代理的一个方面,假设使用它来完成自动设置默认不提交,启动事务,获取到异常则回滚,正常执行则提交。
如果不使用动态代理,则需要在每个方法本身里面设置Connection,写try,catch语句,重复的工作。
为什么要使用动态代理?
我们的业务层可以更加专注于业务本身,把其他相关的活抽象出来共同处理,如日志处理和异常处理等。这样的代码更干净。
代码示例如下:
import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; interface DAO { public Connection GetConn(String url) throws SQLException; public void InsertData(); public void GetData(); public void DeleteData(); } class myops implements DAO { @Override public void InsertData() { System.out.println("inserting data..."); } @Override public void GetData() { System.out.println("getting data..."); } @Override public void DeleteData() { System.out.println("deleting data..."); } @Override public Connection GetConn(String url) throws SQLException { try { Class.forName("oracle.jdbc.driver.OracleDriver"); } catch (ClassNotFoundException e) { e.printStackTrace(); } Connection conn = null; conn = DriverManager .getConnection("jdbc:oracle:thin:@hostip:port:dbname", "system", "pwd"); return conn; } } class dynamicalproxy implements InvocationHandler { Object proxied; Connection conn; public dynamicalproxy(Object _proxied, Connection _conn) { proxied = _proxied; conn = _conn; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { Object rtv = null; conn.setAutoCommit(false); System.out.println("doing something before what ..."); try { rtv = method.invoke(proxied, args); } catch (Exception ex) { conn.rollback(); ex.printStackTrace(); } finally { conn.commit(); System.out.println("commit tran ..."); } System.out.println("doing something after what ..."); return rtv; } } public class proxydemo { public static void main(String[] args) throws IllegalArgumentException, SQLException { myops test = new myops(); DAO dao = (DAO) Proxy.newProxyInstance(DAO.class.getClassLoader(), new Class[] { DAO.class }, new dynamicalproxy(test, test.GetConn(""))); dao.InsertData(); dao.GetData(); dao.DeleteData(); } }
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原文地址:http://www.cnblogs.com/huaxiaoyao/p/4304635.html