如果你想知道java annotation是什麼？你可以先看看：“http://www.infoq.com/articles/Annotation-Hammer”
下面是我做的一個demo：
項目結構：
運行效果：
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程式碼部分：
註：很多人會考慮這個問題，「這樣做的目的是什麼？我們可以做一個設定檔（xml，properties等），不是比這個跟方便...或者說
直接把我們的設定資訊寫入程式...這樣也不會去解析我們寫的註解..”
但是annotation和xml，properties等設定檔的優缺點是什麼呢..
個人觀點：寫註解的時候，比較方便...可以提高開發的效率.有用到註釋的框架，如：Hibernate，Struts，Spring等
回到原話題，「這樣做的目的是什麼？」---這裡只是做一個demo，讓大家知道annotation是怎麼一回事兒....在很多我們開發的
過程中，很少用到我們自己定義的註解(Annotation),如果真的用到了，那麼這篇blog也許就有幫助了..^_^
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/java_annotation/src/com/b510/hongten/annotation/JDBCAnnotation.java
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 "";
}
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載入註解完成...");
}
}
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;
}
}
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));
}
// 關閉記錄集
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
// 關閉聲明
if (ps != null) {
try {
ps.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
// 關閉連結對象
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}