- 自动初始化
- 自动增长
- 自动缩减
第一步，确保数据连接池单例加载
public class ConnectionPool {
//需要单例创建的连接池
private static volatile ConnectionPool pool;
//私有化构造
private ConnectionPool() {
if(pool != null) {
throw new RuntimeException("连接池不可重复创建");
}
}
//懒汉双检锁
public static ConnectionPool getPool() {
if(pool==null) {
synchronized (ConnectionPool.class) {
if(pool==null) {
pool = new ConnectionPool();
}
}
}
return pool;
}
}第二步，加载数据库连接信息，读取配置文件
public class ConnectionPool {
//其余的成员变量：数据库连接信息
private static String driver; //驱动
private static String username; //用户名
private static String password; //密码
private static String url; //数据库连接地址
//初始数据库连接数
private static int initCount = 5;
//最小连接数量
private static int minCount = 3;
//最大连接数量
private static int maxCount = 15;
//存放连接的集合
private static LinkedList pollCollection = new LinkedList<Connection>();
static {
//静态加载配置文件信息
Properties properties = new Properties();
try {
//读取配置文件
properties.load(ConnectionPool.class.getClassLoader()
.getResourceAsStream("jdbcconfig.properties"));
//赋值
driver = properties.getProperty("jdbc.driver");
username = properties.getProperty("jdbc.username");
password = properties.getProperty("jdbc.password");
url = properties.getProperty("jdbc.url");
//如果不设置最大最小连接数，则使用默认配置
try {
initCount = new Integer(properties.getProperty("jdbc.initCount"));
} catch (NumberFormatException e) {
initCount = 5;
System.out.println("initCount使用默认值");
}
try {
minCount = new Integer(properties.getProperty("jdbc.minCount"));
} catch (NumberFormatException e) {
minCount = 3;
System.out.println("minCount使用默认值");
}
try {
maxCount = new Integer(properties.getProperty("jdbc.maxCount"));
} catch (NumberFormatException e) {
maxCount = 5;
System.out.println("maxCount使用默认值");
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
初始化连接池
/**
* 初始化连接池
* @return
*/
private void initPool() {
for(int i = 0;i<initCount;i++) {
boolean flag = pollCollection.add(creat());
if(flag==true) {
currentCount++;
}
}
}
/**
*
* @return 数据库创建连接
*/
private Connection creat() {
try {
//加载驱动
Class.forName(driver);
//建立连接
Connection connection = DriverManager.getConnection(url, username, password);
return connection;
} catch (Exception e) {
throw new RuntimeException("连接创建失败:"+e.getMessage());
}
}自动增长
/**
* 连接自动增长，在池中没有连接时调用
*/
public synchronized void addAuto() {
if(currentCount==maxCount) { //判断当前连接是否达到最大值
throw new RuntimeException("当前连接数已达到最大值");
}
//增长步长为2
for(int i = 0;i<2;i++) {//判断当前连接是否达到最大值
if(currentCount == maxCount) {
break;
}
poolCollection.add(creat());
currentCount++;
}
}获取池中连接
/**
* 获取池中连接
* @return
*/
public Connection getConn() {
if(poolCollection.size()>0) {
return poolCollection.removeFirst();
}
if(currentCount < maxCount) {
addAuto();
return getConn();//递归调用自身
}
//如果当前连接数已经达到最大，等一会再获取
if(currentCount==maxCount) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return getConn(); //递归
}池中连接自动缩减的方法
/**
* 自动缩减连接
*/
public void reduce() {
// 如果当前连接数量大于最小连接数
// 并且池中有空闲连接
if (currentCount > minCount && poolCollection.size() > 0) {
Connection con = poolCollection.removeFirst();
try {
con.close();
con = null;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}还回连接
/**
* 还回连接
* @param conn
*/
public void returnConn(Connection conn) {
poolCollection.add(conn);
reduce();
}整体代码
package jdbctest;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.LinkedList;
import java.util.Properties;
import java.util.concurrent.ConcurrentLinkedQueue;
public class ConnectionPool {
// 需要单例创建的连接池
private static volatile ConnectionPool pool;
// 其余的成员变量：数据库连接信息
private static String driver;
private static String username;
private static String password;
private static String url;
// 初始数据库连接数
private static int initCount = 5;
// 最小连接数量
private static int minCount = 3;
// 最大连接数量
private static int maxCount = 15;
private static int currentCount = 0;
private static LinkedList<Connection> poolCollection = new LinkedList<Connection>();
static {
// 静态加载配置文件信息
Properties properties = new Properties();
try {
properties.load(ConnectionPool.class.getClassLoader().getResourceAsStream("jdbcconfig.properties"));
driver = properties.getProperty("jdbc.driver");
username = properties.getProperty("jdbc.username");
password = properties.getProperty("jdbc.password");
url = properties.getProperty("jdbc.url");
try {
initCount = new Integer(properties.getProperty("jdbc.initCount"));
} catch (NumberFormatException e) {
initCount = 5;
System.out.println("initCount使用默认值");
}
try {
minCount = new Integer(properties.getProperty("jdbc.minCount"));
} catch (NumberFormatException e) {
minCount = 3;
System.out.println("minCount使用默认值");
}
try {
maxCount = new Integer(properties.getProperty("jdbc.maxCount"));
} catch (NumberFormatException e) {
maxCount = 5;
System.out.println("maxCount使用默认值");
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private ConnectionPool() {
if (pool != null) {
throw new RuntimeException("连接池不可重复创建");
}
//初始化连接池
initPool();
}
public static ConnectionPool getPool() {
if (pool == null) {
synchronized (ConnectionPool.class) {
if (pool == null) {
pool = new ConnectionPool();
}
}
}
return pool;
}
/**
* 初始化连接池
*
* @return
*/
private void initPool() {
for (int i = 0; i < initCount; i++) {
boolean flag = poolCollection.add(creat());
if (flag == true) {
currentCount++;
}
}
}
/**
*
* @return 数据库创建连接
*/
private Connection creat() {
try {
// 加载驱动
Class.forName(driver);
// 建立连接
Connection connection = DriverManager.getConnection(url, username, password);
return connection;
} catch (Exception e) {
throw new RuntimeException("连接创建失败:" + e.getMessage());
}
}
/**
* 返回连接池中数量
*
* @return
*/
public int getCount() {
return currentCount;
}
/**
* 连接自动增长
*/
public synchronized void addAuto() {
if (currentCount == maxCount) { // 判断当前连接是否达到最大值
throw new RuntimeException("当前连接数已达到最大值");
}
// 增长步长为2
for (int i = 0; i < 2; i++) {// 判断当前连接是否达到最大值
if (currentCount == maxCount) {
break;
}
poolCollection.add(creat());
currentCount++;
}
}
/**
* 获取池中连接
*
* @return
*/
public Connection getConn() {
if (poolCollection.size() > 0) {
return poolCollection.removeFirst();
}
if (currentCount < maxCount) {
addAuto();//连接池自动增长
return getConn();// 递归调用自身
}
// 如果当前连接数已经达到最大，等一会再获取
if (currentCount == maxCount) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return getConn();
}
/**
* 自动缩减连接
*/
public void reduce() {
// 如果当前连接数量大于最小连接数
// 并且池中有空闲连接
if (currentCount > minCount && poolCollection.size() > 0) {
Connection con = poolCollection.removeFirst();
try {
con.close();
con = null;
currentCount--;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
/**
* 还回连接
* @param conn
*/
public void returnConn(Connection conn) {
poolCollection.add(conn);
reduce();
}
}
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.username=root
jdbc.password=root
jdbc.url=jdbc:mysql://localhost:3306/database
jdbc.initCount=8
jdbc.maxCount=15
...
