一种连接池的实现方案(一)

DB.java

package wkx.db;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class DB {

public static int executeUpdate(String sql) {
int ans = 0;
Connection conn = DB.getConn();
Statement stmt = DB.getStmt(conn);
try {
ans = stmt.executeUpdate(sql);
} catch (SQLException e) {
e.printStackTrace();
}finally{
DB.close(stmt);
DB.close(conn);
}
return ans;
}

public static Connection getConn() {
return ConnPool.getConn();
}

public static Statement getStmt(Connection conn) {
Statement stmt = null;
try {
stmt = conn.createStatement();
} catch (SQLException e) {
e.printStackTrace();
}
return stmt;
}



public static ResultSet executeQuery(Statement stmt, String sql) {
//System.out.println("QUERY:"+sql);
ResultSet rs = null;
try {
rs = stmt.executeQuery(sql);
} catch (SQLException e) {
e.printStackTrace();
}
return rs;
}

public static void close(Connection conn) {
ConnPool.close(conn);
}

public static void close(Statement stmt) {
try {
if (stmt != null) {
stmt.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
stmt = null;
}

public static void close(ResultSet rs) {
try {
if (rs != null) {
rs.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
rs = null;
}

public static void closeAll(Connection conn,Statement stmt){
DB.close(conn);
DB.close(stmt);
}

public static void closeAll(Connection conn,Statement stmt,ResultSet rs){
DB.close(conn);
DB.close(stmt);
DB.close(rs);
}

}

ConnPool.java

[java]
package wkx.db;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.LinkedList;

public class ConnPool {

public static final int MAX_CONN_NUM = 10;
private static LinkedList conns = null;
private static int connNum = 0;

static {
conns = new LinkedList();
}

private ConnPool(){

}

public static Connection getConn() {
Connection conn = null;
if(conns.size()==0){
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/project", "root", "root");
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
connNum++;
}else{
conn=conns.pop();
}
/**
*
*/
ConnPool.printStatus();
return conn;
}

public static void close(Connection conn) {
if(connNum>ConnPool.MAX_CONN_NUM){
try {
if (conn != nu