Java Annotation(Java 注解)的实现代码
如果你想知道java annotation是什么？你可以先看看：“http://www.infoq.com/articles/Annotation-Hammer”
下面是我做的一个demo：
项目结构：
运行效果：
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代码部分：
注：很多人会考虑这个问题，“这样做的目的是什么？我们可以做一个配置文件（xml，properties等），不是比这个跟方便...或者说
直接把我们的配置信息写入程序...这样也不会去解析我们写的注释..”
但是annotation和xml，properties等配置文件的优缺点是什么呢..
个人观点：写注释的时候，比较方便...可以提高开发的效率.有用到注释的框架，如：Hibernate，Struts，Spring等
回到原话题，“这样做的目的是什么？“---这里只是做一个demo，让大家知道annotation是怎么一回事儿....在很多我们开发的
过程中，很少用到我们自己定义的注释(Annotation),如果真的用到了，那么这篇blog也许就有帮助了..^_^
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/java_annotation/src/com/b510/hongten/annotation/JDBCAnnotation.java 代码如下:
/** * */ package com.b510.hongten.annotation; import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; /** * JDBC annotation * * @author Hongten * @date 2013-4-10 */ @Documented @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.TYPE) public @interface JDBCAnnotation { String driver() default "com.mysql.jdbc.Driver"; String dbName() default ""; String encoding() default "UTF-8"; String port() default "3306"; String host() default "localhost"; String userName() default "root"; String password() default ""; }
/java_annotation/src/com/b510/hongten/jdbc/JDBCUtil.java 代码如下:
/** * */ package com.b510.hongten.jdbc; import com.b510.hongten.annotation.JDBCAnnotation; /** * @author Hongten * @date 2013-4-12 */ @JDBCAnnotation(dbName = "db_lucene", port = "3306", host = "192.168.0.119", userName = "root", password = "root") public class JDBCUtil { private static String driver; private static String dbName; private static String encoding; private static String port; private static String host; private static String passwrod; private static String userName; private static String url; public void checkInterceptor(Class<?> cl) throws Exception { boolean flag = cl.isAnnotationPresent(JDBCAnnotation.class); if (flag) { JDBCAnnotation jdbcAnnotation = cl.getAnnotation(JDBCAnnotation.class); driver = jdbcAnnotation.driver(); dbName = jdbcAnnotation.dbName(); encoding = jdbcAnnotation.encoding(); port = jdbcAnnotation.port(); host = jdbcAnnotation.host(); userName = jdbcAnnotation.userName(); passwrod = jdbcAnnotation.password(); url = "jdbc:mysql://" + host + ":" + port + "/" + dbName + "?characterEncoding=" + encoding; System.out.println("JDBCUtil加载注释完成..."); } } public JDBCUtil() { try { checkInterceptor(JDBCUtil.class); } catch (Exception e) { e.printStackTrace(); } } public static String getDriver() { return driver; } public static void setDriver(String driver) { JDBCUtil.driver = driver; } public static String getDbName() { return dbName; } public static void setDbName(String dbName) { JDBCUtil.dbName = dbName; } public static String getEncoding() { return encoding; } public static void setEncoding(String encoding) { JDBCUtil.encoding = encoding; } public static String getPort() { return port; } public static void setPort(String port) { JDBCUtil.port = port; } public static String getHost() { return host; } public static void setHost(String host) { JDBCUtil.host = host; } public static String getPasswrod() { return passwrod; } public static void setPasswrod(String passwrod) { JDBCUtil.passwrod = passwrod; } public static String getUserName() { return userName; } public static void setUserName(String userName) { JDBCUtil.userName = userName; } public static String getUrl() { return url; } public static void setUrl(String url) { JDBCUtil.url = url; } }
/java_annotation/src/com/b510/hongten/jdbc/JDBCTest.java 代码如下:
/** * */ package com.b510.hongten.jdbc; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; /** * * @author Hongten</br> * @date 2012-7-16 * */ public class JDBCTest { @SuppressWarnings("static-access") public static void main(String[] args) { JDBCUtil jdbcUtil = new JDBCUtil(); String sql = "select * from mymails"; try { Class.forName(jdbcUtil.getDriver()); Connection conn = DriverManager.getConnection(jdbcUtil.getUrl(), jdbcUtil.getUserName(), jdbcUtil.getPasswrod()); PreparedStatement ps = conn.prepareStatement(sql); ResultSet rs = ps.executeQuery(); while (rs.next()) { System.out.println("id : " + rs.getInt(1) + " name : " + rs.getString(2) + " mail : " + rs.getString(3)); } // 关闭记录集 if (rs != null) { try { rs.close(); } catch (SQLException e) { e.printStackTrace(); } } // 关闭声明 if (ps != null) { try { ps.close(); } catch (SQLException e) { e.printStackTrace(); } } // 关闭链接对象 if (conn != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } catch (Exception e) { e.printStackTrace(); } } }
以上是 Java Annotation(Java 注解)的实现代码 的全部内容，
来源链接：
utcz.com/p/207828.html
