package blog.util;
 
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;
 
import blog.exception.DBException;
 
 
public class DBUtil {
     
    private static DataSource ds = null;
 
    /**
     * 從資料庫連線池獲得一個數據庫連線
     * @return 資料庫連線
     * @throws DBException
     */
    public static Connection getConnection() throws DBException {
         
        //用資料庫連線池的方式實現,JNDI
        try {
            if(ds == null){        
                Context context = new InitialContext();
                ds = (DataSource) context.lookup("java:comp/env/jdbc/pmdb");           
            }
             
            return ds.getConnection();
        } catch (NamingException e) {          
            throw new DBException("資料庫連線池查詢失敗", e);
        } catch (SQLException e) {         
            throw new DBException("獲取資料庫連線異常", e);
        }
       
    }
     
    public static PreparedStatement getPreparedStatement(Connection conn, String sql) throws DBException {
        PreparedStatement pstmt = null;
        try {
            if (conn != null) {
                pstmt = conn.prepareStatement(sql);
            }
        } catch (SQLException e) {
            throw new DBException("建立執行語句失敗", e);
        }
        return pstmt;
    }
 
    public static PreparedStatement getPreparedStatement(Connection conn, String sql, int autoGenereatedKeys) throws DBException {
        PreparedStatement pstmt = null;
        try {
            if (conn != null) {
                pstmt = conn.prepareStatement(sql, autoGenereatedKeys);
            }
        } catch (SQLException e) {
            throw new DBException("建立執行語句失敗", e);
        }
        return pstmt;
    }
 
    public static Statement getStatement(Connection conn) throws DBException {
        Statement stmt = null;
        try {
            if (conn != null) {
                stmt = conn.createStatement();
            }
        } catch (SQLException e) {
            throw new DBException("建立執行語句失敗", e);
        }
        return stmt;
    }
 
    public static ResultSet getResultSet(Statement stmt, String sql) throws DBException {
        ResultSet rs = null;
        try {
            if (stmt != null) {
                rs = stmt.executeQuery(sql);
            }
        } catch (SQLException e) {
            throw new DBException("獲得查詢結果集失敗：" + sql, e);
        }
        return rs;
    }
 
    public static void executeUpdate(Statement stmt, String sql) throws DBException {
        try {
            if (stmt != null) {
                stmt.executeUpdate(sql);
            }
        } catch (SQLException e) {
            throw new DBException("更新失敗：" + sql, e);
        }
    }
 
    /**
     * 歸還資料庫連線
     * @param conn 資料庫連線例項
     * @throws DBException
     */
    public static void close(Connection conn) throws DBException {
        try {
            if (conn != null) {
                conn.close(); //把資料庫連線歸還到資料庫連線池，並不是真正的斷開資料庫的連線
            }
        } catch (SQLException e) {
            throw new DBException("關閉資料庫連線異常", e);
        }
    }
 
    public static void close(Statement stmt) throws DBException {
        try {
            if (stmt != null) {
                stmt.close();
                stmt = null;
            }
        } catch (SQLException e) {
            throw new DBException("關閉資料庫語句異常", e);
        }
    }
 
    public static void close(ResultSet rs) throws DBException {
        try {
            if (rs != null) {
                rs.close();
                rs = null;
            }
        } catch (SQLException e) {
            throw new DBException("關閉資料庫結果集異常", e);
        }
    }
}
 

<Context reloadable="true">
    <Resource name="jdbc/pmdb" auth="Container" type="javax.sql.DataSource"
    maxActive="100" maxIdle="30" maxWait="10000"
    username="root" password="1234"
    driverClassName="com.mysql.jdbc.Driver"
    url="jdbc:mysql://localhost:3306/pmdb?useUnicode=true&characterEncoding=utf-8">
    </Resource>
</Context>
 

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee   http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
 
 <resource-ref>
  <res-ref-name>jdbc/pmdb</res-ref-name>
  <res-type>javax.sql.DataSource</res-type>
  <res-auth>Container</res-auth>
 </resource-ref>
 
</web-app>