If you want to know what is java annotation? You can take a look first: "http://www.infoq.com/articles/Annotation-Hammer"
Here is a demo I made:
Project structure:
Operation effect:
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Code part:
Note: Many people will consider this question, "What is the purpose of doing this? We can make a configuration file (xml, properties, etc.), which is not more convenient than this... or
Write our configuration information directly into the program... This way the comments we wrote will not be parsed.."
But what are the advantages and disadvantages of annotation and configuration files such as xml and properties?
Personal opinion: When writing comments, it is more convenient...it can improve the efficiency of development. Annotation frameworks are useful, such as: Hibernate, Struts, Spring, etc.
Back to the original topic, "What is the purpose of doing this?"---This is just a demo to let everyone know what annotation is all about.... In many of the projects we develop
In the process, our own defined annotations are rarely used. If they are really used, then this blog may be helpful..^_^
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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 loading comments completed...");
}
}
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));
}
//Close the recordset
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
// close statement
if (ps != null) {
try {
ps.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
// Close the link object
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}