package com.demo.db;
import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;
public class DBConnectionManager {
static private DBConnectionManager instance; // 唯一實例
static private int clients;
private Vector drivers = new Vector();
private Hashtable pools = new Hashtable();
/**
* 將文本信息在後臺打印出來
*/
private void log(String msg) {
System.out.println(new Date() + ": " + msg);
}
/**
* 返回唯一實例.如果是第一次調用此方法,則創建實例
*
* @return DBConnectionManager 唯一實例
*/
static synchronized public DBConnectionManager getInstance() {
if (instance == null) {
instance = new DBConnectionManager();
}
clients++;
return instance;
}
/**
* 建構函數私有以防止其它對象創建本類實例
*/
private DBConnectionManager() {
init();
}
/**
* 將連接對象返回給由名字指定的連接池
*
* @param name
* 在屬性文件中定義的連接池名字
* @param con
* 連接對象
*/
public void freeConnection(String name, Connection con) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
pool.freeConnection(con);
}
}
/**
* 獲得一個可用的(空閒的)連接.如果沒有可用連接,且已有連接數小於最大連接數 限制,則創建並返回新連接
*
* @param name
* 在屬性文件中定義的連接池名字
* @return Connection 可用連接或null
*/
public Connection getConnection(String name) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
return pool.getConnection();
}
return null;
}
/**
* 獲得一個可用連接.若沒有可用連接,且已有連接數小於最大連接數限制, 則創建並返回新連接.否則,在指定的時間內等待其它線程釋放連接.
*
* @param name
* 連接池名字
* @param time
* 以毫秒計的等待時間
* @return Connection 可用連接或null
*/
public Connection getConnection(String name, long time) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
return pool.getConnection(time);
}
return null;
}
/**
* 關閉所有連接,撤銷驅動程序的註冊
*/
public synchronized void release() {
// 等待直到最後一個客戶程序調用
if (--clients != 0) {
return;
}
Enumeration allPools = pools.elements();
while (allPools.hasMoreElements()) {
DBConnectionPool pool = (DBConnectionPool) allPools.nextElement();
pool.release();
}
Enumeration allDrivers = drivers.elements();
while (allDrivers.hasMoreElements()) {
Driver driver = (Driver) allDrivers.nextElement();
try {
DriverManager.deregisterDriver(driver);
log("撤銷JDBC驅動程序 " + driver.getClass().getName() + "的註冊");
} catch (SQLException e) {
log("無法撤銷下列JDBC驅動程序的註冊: " + driver.getClass().getName());
}
}
}
/**
* 根據指定屬性創建連接池實例.
*
* @param props
* 連接池屬性
*/
private void createPools(Properties props) {
Enumeration propNames = props.propertyNames();
while (propNames.hasMoreElements()) {
String name = (String) propNames.nextElement();
if (name.endsWith(".url"))
{
String poolName = "sqlserver";
String url = props.getProperty(poolName + ".url");
if (url == null)
{
log("沒有爲連接池" + poolName + "指定URL");
continue;
}
String user = props.getProperty(poolName + ".user");
String password = props.getProperty(poolName + ".password");
String maxconn = props.getProperty(poolName + ".maxconn", "0");
int max;
try {
max = Integer.valueOf(maxconn).intValue();
} catch (NumberFormatException e) {
log("錯誤的最大連接數限制: " + maxconn + " .連接池: " + poolName);
max = 0;
}
DBConnectionPool pool = new DBConnectionPool(poolName, url,
user, password, max);
pools.put(poolName, pool);
log("成功創建連接池" + poolName);
}
}
}
/**
* 讀取屬性完成初始化
*/
private void init() {
InputStream is = getClass().getResourceAsStream("/YYZL_db.properties");
Properties dbProps = new Properties();
try {
dbProps.load(is);
} catch (Exception e) {
log("不能讀取屬性文件.請確保db.properties在CLASSPATH指定的路徑中");
return;
}
loadDrivers(dbProps);
createPools(dbProps);
}
/**
* 裝載和註冊所有JDBC驅動程序
*
* @param props
* 屬性
*/
private void loadDrivers(Properties props) {
String driverClasses = props.getProperty("driver");
StringTokenizer st = new StringTokenizer(driverClasses);
while (st.hasMoreElements()) {
String driverClassName = st.nextToken().trim();
try {
Driver driver = (Driver) Class.forName(driverClassName)
.newInstance();
DriverManager.registerDriver(driver);
drivers.addElement(driver);
log("成功註冊JDBC驅動程序" + driverClassName);
} catch (Exception e) {
log("無法註冊JDBC驅動程序: " + driverClassName + ", 錯誤: " + e);
}
}
}
/**
* 此內部類定義了一個連接池.它能夠根據要求創建新連接,直到預定的最大連接數爲止.在返回連接給客戶程序之前,它能夠驗證連接的有效性.
*/
class DBConnectionPool {
private int userCount;
private Vector freeConnections = new Vector();
private int maxConn;
private String name;
private String password;
private String URL;
private String user;
// private String databaseUrl;
/**
* 創建新的連接池
*
* @param name
* 連接池名字
* @param URL
* 數據庫的JDBC URL
* @param user
* 數據庫帳號,或 null
* @param password
* 密碼,或 null
* @param maxConn
* 此連接池允許建立的最大連接數
*/
public DBConnectionPool(String name, String URL, String user,
String password, int maxConn) {
this.name = name;
this.URL = URL;
this.user = user;
this.password = password;
this.maxConn = maxConn;
}
/**
* 將不再使用的連接返回給連接池
*
* @param con
* 客戶程序釋放的連接
*/
public synchronized void freeConnection(Connection con) {
// 將指定連接加入到向量末尾
freeConnections.addElement(con);
userCount--;
notifyAll();
}
/**
* 從連接池獲得一個可用連接.如沒有空閒的連接且當前連接數小於最大連接 數限制,則創建新連接.如原來登記爲可用的連接不再有效,則從向量刪除之,
* 然後遞歸調用自己以嘗試新的可用連接.
*/
public synchronized Connection getConnection() {
Connection con = null;
if (freeConnections.size() > 0) {
// 獲取向量中第一個可用連接
con = (Connection) freeConnections.firstElement();
freeConnections.removeElementAt(0);
try {
if (con.isClosed()) {
log("從連接池" + name + "刪除一個無效連接");
// 遞歸調用自己,嘗試再次獲取可用連接
con = getConnection();
}
} catch (SQLException e) {
log("從連接池" + name + "刪除一個無效連接");
// 遞歸調用自己,嘗試再次獲取可用連接
con = getConnection();
}
} else if (maxConn == 0 || userCount < maxConn) {
con = newConnection();
}
if (con != null) {
userCount++;
}
return con;
}
/**
* 從連接池獲取可用連接.可以指定客戶程序能夠等待的最長時間 參見前一個getConnection()方法.
*
* @param timeout
* 以毫秒計的等待時間限制
*/
public synchronized Connection getConnection(long timeout) {
long startTime = new Date().getTime();
Connection con;
while ((con = getConnection()) == null) {
try {
wait(timeout);
} catch (InterruptedException e) {
}
if ((new Date().getTime() - startTime) >= timeout) {
// wait()返回的原因是超時
return null;
}
}
return con;
}
/**
* 關閉所有連接
*/
public synchronized void release() {
Enumeration allConnections = freeConnections.elements();
while (allConnections.hasMoreElements()) {
Connection con = (Connection) allConnections.nextElement();
try {
con.close();
log("關閉連接池" + name + "中的一個連接");
} catch (SQLException e) {
log("無法關閉連接池" + name + "中的連接");
}
}
freeConnections.removeAllElements();
}
/**
* 創建新的連接
*/
private Connection newConnection() {
Connection con = null;
try {
if (user == null) {
con = DriverManager.getConnection(URL);
} else {
con = DriverManager.getConnection(URL, user, password);
}
log("連接池" + name + "創建一個新的連接");
} catch (SQLException e) {
log("無法創建下列URL的連接: " + URL);
return null;
}
return con;
}
}
}
package com.demo.db;
import java.sql.*;
public class DBConnect {
private Connection conn = null;
private Statement stmt = null;
private PreparedStatement prepstmt = null;
private DBConnectionManager dcm = null;
void init() {
dcm = DBConnectionManager.getInstance();
conn = dcm.getConnection("mysql");
}
/**
* 構造數據庫的連接和訪問類
*/
public DBConnect() throws Exception {
init();
stmt = conn.createStatement();
}
public DBConnect(int resultSetType, int resultSetConcurrency)
throws Exception {
init();
stmt = conn.createStatement(resultSetType, resultSetConcurrency);
}
/**
* 構造數據庫的連接和訪問類 預編譯SQL語句
*
* @param sql
* SQL語句
*/
public DBConnect(String sql) throws Exception {
init();
this.prepareStatement(sql);
}
public DBConnect(String sql, int resultSetType, int resultSetConcurrency)
throws Exception {
init();
this.prepareStatement(sql, resultSetType, resultSetConcurrency);
}
/**
* 返回連接
*
* @return Connection 連接
*/
public Connection getConnection() {
return conn;
}
/**
* PreparedStatement
*
* @param sql 預設SQL語句
*/
public void prepareStatement(String sql) throws SQLException {
prepstmt = conn.prepareStatement(sql);
}
public void prepareStatement(String sql, int resultSetType,
int resultSetConcurrency) throws SQLException {
prepstmt = conn.prepareStatement(sql, resultSetType,
resultSetConcurrency);
}
/**
* 設置對應值
*
* @param index
* 參數索引
* @param value
* 對應值
*/
public void setString(int index, String value) throws SQLException {
prepstmt.setString(index, value);
}
public void setInt(int index, int value) throws SQLException {
prepstmt.setInt(index, value);
}
public void setBoolean(int index, boolean value) throws SQLException {
prepstmt.setBoolean(index, value);
}
public void setDate(int index, Date value) throws SQLException {
prepstmt.setDate(index, value);
}
public void setTimestamp(int index, Timestamp value) throws SQLException {
prepstmt.setTimestamp(index, value);
}
public void setLong(int index, long value) throws SQLException {
prepstmt.setLong(index, value);
}
public void setFloat(int index, float value) throws SQLException {
prepstmt.setFloat(index, value);
}
public void setBytes(int index, byte[] value) throws SQLException {
prepstmt.setBytes(index, value);
}
public void clearParameters() throws SQLException {
prepstmt.clearParameters();
prepstmt = null;
}
/**
* 返回預設狀態
*/
public PreparedStatement getPreparedStatement() {
return prepstmt;
}
/**
* 返回狀態
*
* @return Statement 狀態
*/
public Statement getStatement() {
return stmt;
}
/**
* 執行SQL語句返回字段集
*
* @param sql
* SQL語句
* @return ResultSet 字段集
*/
public ResultSet executeQuery(String sql) throws SQLException {
if (stmt != null) {
return stmt.executeQuery(sql);
} else
return null;
}
public ResultSet executeQuery() throws SQLException {
if (prepstmt != null) {
return prepstmt.executeQuery();
} else
return null;
}
/**
* 執行SQL語句
*
* @param sql
* SQL語句
*/
public void executeUpdate(String sql) throws SQLException {
if (stmt != null)
stmt.executeUpdate(sql);
}
public void executeUpdate() throws SQLException {
if (prepstmt != null)
prepstmt.executeUpdate();
}
/**
* 關閉連接
*/
public void close() throws Exception {
if (stmt != null) {
stmt.close();
stmt = null;
}
if (prepstmt != null) {
prepstmt.close();
prepstmt = null;
}
if (conn != null) {
dcm.freeConnection("mysql", conn);
}
}
}
//屬性文件
db.properties
driver=com.mysql.jdbc.Driver
mysql.url=jdbc:mysql://192.168.23.176:3306/YYZL?useUnicode=true&characterEncoding=utf8
mysql.user=root
mysql.password=123456
mysql.maxconn=2000
