【愚公系列】2023年05月 Java教学课程 113-JDBC的（数据库连接池）
一、数据库连接池
1.数据库连接池的概念
数据库连接池是一种用于管理数据库连接的技术，它可以在应用程序启动时创建一定数量的数据库连接，然后将这些连接放入一个连接池中，当应用程序需要访问数据库时，就从连接池中获取一个连接，并在使用完毕后将连接归还给连接池。这样可以避免频繁地创建和销毁数据库连接，从而提高数据库访问效率和性能。数据库连接池通常包含以下属性：最小连接数、最大连接数、连接超时时间、空闲连接回收时间等。
数据库连接池原理图
2.自定义连接池
• java.sql.DataSource接口：数据源(数据库连接池)。java官方提供的数据库连接池规范(接口)
– 获取数据库连接对象：Connection getConnection();
• 自定义连接池
package com.itheima.utils;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
/*
JDBC工具类
*/
public class JDBCUtils {
//1.私有构造方法
private JDBCUtils(){};
//2.声明配置信息变量
private static String driverClass;
private static String url;
private static String username;
private static String password;
private static Connection con;
//3.静态代码块中实现加载配置文件和注册驱动
static{
try{
//通过类加载器返回配置文件的字节流
InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("config.properties");
//创建Properties集合，加载流对象的信息
Properties prop = new Properties();
prop.load(is);
//获取信息为变量赋值
driverClass = prop.getProperty("driverClass");
url = prop.getProperty("url");
username = prop.getProperty("username");
password = prop.getProperty("password");
//注册驱动
Class.forName(driverClass);
} catch (Exception e) {
e.printStackTrace();
}
}
//4.获取数据库连接的方法
public static Connection getConnection() {
try {
con = DriverManager.getConnection(url,username,password);
} catch (SQLException e) {
e.printStackTrace();
}
return con;
}
//5.释放资源的方法
public static void close(Connection con, Statement stat, ResultSet rs) {
if(con != null) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(stat != null) {
try {
stat.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public static void close(Connection con, Statement stat) {
close(con,stat,null);
}
}
package itheima01;
import com.itheima.utils.JDBCUtils;
import javax.sql.DataSource;
import java.io.PrintWriter;
import java.sql.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.logging.Logger;
/*
自定义连接池类
*/
public class MyDataSource implements DataSource {
//定义集合容器，用于保存多个数据库连接对象
private static List<Connection> pool = Collections.synchronizedList(new ArrayList<Connection>());
//静态代码块，生成10个数据库连接保存到集合中
static {
for (int i = 0; i < 10; i++) {
Connection con = JDBCUtils.getConnection();
pool.add(con);
}
}
//返回连接池的大小
public int getSize() {
return pool.size();
}
//从池中返回一个数据库连接
@Override
public Connection getConnection() {
if(pool.size() > 0) {
//从池中获取数据库连接
return pool.remove(0);
}else {
throw new RuntimeException("连接数量已用尽");
}
}
@Override
public Connection getConnection(String username, String password) throws SQLException {
return null;
}
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
return null;
}
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
return false;
}
@Override
public PrintWriter getLogWriter() throws SQLException {
return null;
}
@Override
public void setLogWriter(PrintWriter out) throws SQLException {
}
@Override
public void setLoginTimeout(int seconds) throws SQLException {
}
@Override
public int getLoginTimeout() throws SQLException {
return 0;
}
@Override
public Logger getParentLogger() throws SQLFeatureNotSupportedException {
return null;
}
}
3.自定义连接池测试
package itheima01;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
public class MyDataSourceTest {
public static void main(String[] args) throws Exception{
//1.创建连接池对象
MyDataSource dataSource = new MyDataSource();
System.out.println("使用之前的数量：" + dataSource.getSize());
//2.通过连接池对象获取连接对象
Connection con = dataSource.getConnection();
System.out.println(con.getClass());
//3.查询学生表的全部信息
String sql = "SELECT * FROM student";
PreparedStatement pst = con.prepareStatement(sql);
//4.执行sql语句，接收结果集
ResultSet rs = pst.executeQuery();
//5.处理结果集
while(rs.next()) {
System.out.println(rs.getInt("sid") + "\t" + rs.getString("name") + "\t" + rs.getInt("age") + "\t" + rs.getDate("birthday"));
}
//6.释放资源
rs.close();
pst.close();
con.close(); // 用完以后，关闭连接
System.out.println("使用之后的数量：" + dataSource.getSize());
}
}
4.归还连接
• 继承(无法解决)
– 通过打印连接对象，发现DriverManager获取的连接实现类是JDBC4Connection。
– 自定义一个类，继承JDBC4Connection这个类，重写close()方法。
/*
自定义Connection类
*/
public class MyConnection1 extends JDBC4Connection {
//声明连接对象和连接池集合对象
private Connection con;
private List<Connection> pool;
//通过构造方法给成员变量赋值
public MyConnection1(String hostToConnectTo, int portToConnectTo, Properties info, String databaseToConnectTo, String url,Connection con,List<Connection> pool) throws SQLException {
super(hostToConnectTo, portToConnectTo, info, databaseToConnectTo, url);
this.con = con;
this.pool = pool;
}
//重写close()方法，将连接归还给池中
@Override
public void close() throws SQLException {
pool.add(con);
}
}
– 但是这种方式行不通，通过查看JDBC工具类获取连接的方法我们发现：我们虽然自定义了一个子类，完成了归还连接的操作。但是DriverManager获取的还是JDBC4Connection这个对象，并不是我们的子类对象。而我们又不能整体去修改驱动包中类的功能！
//将之前的连接对象换成自定义的子类对象
private static MyConnection1 con;
//4.获取数据库连接的方法
public static Connection getConnection() {
try {
//等效于：MyConnection1 con = new JDBC4Connection(); 语法错误！
con = DriverManager.getConnection(url,username,password);
} catch (SQLException e) {
e.printStackTrace();
}
return con;
}
• 装饰设计模式
– 自定义连接类
/*
自定义Connection类。通过装饰设计模式，实现和mysql驱动包中的Connection实现类相同的功能！
实现步骤：
1.定义一个类，实现Connection接口
2.定义Connection连接对象和连接池容器对象的变量
3.提供有参构造方法，接收连接对象和连接池对象，对变量赋值
4.在close()方法中，完成连接的归还
5.剩余方法，只需要调用mysql驱动包的连接对象完成即可
*/
public class MyConnection2 implements Connection {
//2.定义Connection连接对象和连接池容器对象的变量
private Connection con;
private List<Connection> pool;
//3.提供有参构造方法，接收连接对象和连接池对象，对变量赋值
public MyConnection2(Connection con,List<Connection> pool) {
this.con = con;
this.pool = pool;
}
//4.在close()方法中，完成连接的归还
@Override
public void close() throws SQLException {
pool.add(con);
}
@Override
public Statement createStatement() throws SQLException {
return con.createStatement();
}
@Override
public PreparedStatement prepareStatement(String sql) throws SQLException {
return con.prepareStatement(sql);
}
@Override
public CallableStatement prepareCall(String sql) throws SQLException {
return con.prepareCall(sql);
}
@Override
public String nativeSQL(String sql) throws SQLException {
return con.nativeSQL(sql);
}
@Override
public void setAutoCommit(boolean autoCommit) throws SQLException {
con.setAutoCommit(autoCommit);
}
@Override
public boolean getAutoCommit() throws SQLException {
return con.getAutoCommit();
}
@Override
public void commit() throws SQLException {
con.commit();
}
@Override
public void rollback() throws SQLException {
con.rollback();
}
@Override
public boolean isClosed() throws SQLException {
return con.isClosed();
}
@Override
public DatabaseMetaData getMetaData() throws SQLException {
return con.getMetaData();
}
@Override
public void setReadOnly(boolean readOnly) throws SQLException {
con.setReadOnly(readOnly);
}
@Override
public boolean isReadOnly() throws SQLException {
return con.isReadOnly();
}
@Override
public void setCatalog(String catalog) throws SQLException {
con.setCatalog(catalog);
}
@Override
public String getCatalog() throws SQLException {
return con.getCatalog();
}
@Override
public void setTransactionIsolation(int level) throws SQLException {
con.setTransactionIsolation(level);
}
@Override
public int getTransactionIsolation() throws SQLException {
return con.getTransactionIsolation();
}
@Override
public SQLWarning getWarnings() throws SQLException {
return con.getWarnings();
}
@Override
public void clearWarnings() throws SQLException {
con.clearWarnings();
}
@Override
public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
return con.createStatement(resultSetType,resultSetConcurrency);
}
@Override
public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
return con.prepareStatement(sql,resultSetType,resultSetConcurrency);
}
@Override
public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
return con.prepareCall(sql,resultSetType,resultSetConcurrency);
}
@Override
public Map<String, Class<?>> getTypeMap() throws SQLException {
return con.getTypeMap();
}
@Override
public void setTypeMap(Map<String, Class<?>> map) throws SQLException {
con.setTypeMap(map);
}
@Override
public void setHoldability(int holdability) throws SQLException {
con.setHoldability(holdability);
}
@Override
public int getHoldability() throws SQLException {
return con.getHoldability();
}
@Override
public Savepoint setSavepoint() throws SQLException {
return con.setSavepoint();
}
@Override
public Savepoint setSavepoint(String name) throws SQLException {
return con.setSavepoint(name);
}
@Override
public void rollback(Savepoint savepoint) throws SQLException {
con.rollback(savepoint);
}
@Override
public void releaseSavepoint(Savepoint savepoint) throws SQLException {
con.releaseSavepoint(savepoint);
}
@Override
public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
return con.createStatement(resultSetType,resultSetConcurrency,resultSetHoldability);
}
@Override
public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
return con.prepareStatement(sql,resultSetType,resultSetConcurrency,resultSetHoldability);
}
@Override
public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
return con.prepareCall(sql,resultSetType,resultSetConcurrency,resultSetHoldability);
}
@Override
public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
return con.prepareStatement(sql,autoGeneratedKeys);
}
@Override
public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
return con.prepareStatement(sql,columnIndexes);
}
@Override
public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
return con.prepareStatement(sql,columnNames);
}
@Override
public Clob createClob() throws SQLException {
return con.createClob();
}
@Override
public Blob createBlob() throws SQLException {
return con.createBlob();
}
@Override
public NClob createNClob() throws SQLException {
return con.createNClob();
}
@Override
public SQLXML createSQLXML() throws SQLException {
return con.createSQLXML();
}
@Override
public boolean isValid(int timeout) throws SQLException {
return con.isValid(timeout);
}
@Override
public void setClientInfo(String name, String value) throws SQLClientInfoException {
con.setClientInfo(name,value);
}
@Override
public void setClientInfo(Properties properties) throws SQLClientInfoException {
con.setClientInfo(properties);
}
@Override
public String getClientInfo(String name) throws SQLException {
return con.getClientInfo(name);
}
@Override
public Properties getClientInfo() throws SQLException {
return con.getClientInfo();
}
@Override
public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
return con.createArrayOf(typeName,elements);
}
@Override
public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
return con.createStruct(typeName,attributes);
}
@Override
public void setSchema(String schema) throws SQLException {
con.setSchema(schema);
}
@Override
public String getSchema() throws SQLException {
return con.getSchema();
}
@Override
public void abort(Executor executor) throws SQLException {
con.abort(executor);
}
@Override
public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {
con.setNetworkTimeout(executor,milliseconds);
}
@Override
public int getNetworkTimeout() throws SQLException {
return con.getNetworkTimeout();
}
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
return con.unwrap(iface);
}
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
return con.isWrapperFor(iface);
}
}
– 自定义连接池类
public class MyDataSource implements DataSource{
//定义集合容器，用于保存多个数据库连接对象
private static List<Connection> pool = Collections.synchronizedList(new ArrayList<Connection>());
//静态代码块，生成10个数据库连接保存到集合中
static {
for (int i = 0; i < 10; i++) {
Connection con = JDBCUtils.getConnection();
pool.add(con);
}
}
//返回连接池的大小
public int getSize() {
return pool.size();
}
//从池中返回一个数据库连接
@Override
public Connection getConnection() {
if(pool.size() > 0) {
//从池中获取数据库连接
Connection con = pool.remove(0);
//通过自定义连接对象进行包装
MyConnection2 mycon = new MyConnection2(con,pool);
//返回包装后的连接对象
return mycon;
}else {
throw new RuntimeException("连接数量已用尽");
}
}
}
• 适配器设计模式
– 通过之前MyConnection2连接类我们发现，有很多个需要实现的方法。这个时候我们就可以使用适配器设计模式了。提供一个适配器类，实现Connection接口，将所有功能进行实现(除了close方法)。自定义连接类只需要继承这个适配器类，重写需要改进的close()方法即可！
– 适配器类
/*
适配器抽象类。实现Connection接口。
实现所有的方法，调用mysql驱动包中Connection连接对象的方法
*/
public abstract class MyAdapter implements Connection {
// 定义数据库连接对象的变量
private Connection con;
// 通过构造方法赋值
public MyAdapter(Connection con) {
this.con = con;
}
// 所有的方法，均调用mysql的连接对象实现
@Override
public Statement createStatement() throws SQLException {
return con.createStatement();
}
@Override
public PreparedStatement prepareStatement(String sql) throws SQLException {
return con.prepareStatement(sql);
}
@Override
public CallableStatement prepareCall(String sql) throws SQLException {
return con.prepareCall(sql);
}
@Override
public String nativeSQL(String sql) throws SQLException {
return con.nativeSQL(sql);
}
@Override
public void setAutoCommit(boolean autoCommit) throws SQLException {
con.setAutoCommit(autoCommit);
}
@Override
public boolean getAutoCommit() throws SQLException {
return con.getAutoCommit();
}
@Override
public void commit() throws SQLException {
con.commit();
}
@Override
public void rollback() throws SQLException {
con.rollback();
}
@Override
public boolean isClosed() throws SQLException {
return con.isClosed();
}
@Override
public DatabaseMetaData getMetaData() throws SQLException {
return con.getMetaData();
}
@Override
public void setReadOnly(boolean readOnly) throws SQLException {
con.setReadOnly(readOnly);
}
@Override
public boolean isReadOnly() throws SQLException {
return con.isReadOnly();
}
@Override
public void setCatalog(String catalog) throws SQLException {
con.setCatalog(catalog);
}
@Override
public String getCatalog() throws SQLException {
return con.getCatalog();
}
@Override
public void setTransactionIsolation(int level) throws SQLException {
con.setTransactionIsolation(level);
}
@Override
public int getTransactionIsolation() throws SQLException {
return con.getTransactionIsolation();
}
@Override
public SQLWarning getWarnings() throws SQLException {
return con.getWarnings();
}
@Override
public void clearWarnings() throws SQLException {
con.clearWarnings();
}
@Override
public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
return con.createStatement(resultSetType,resultSetConcurrency);
}
@Override
public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
return con.prepareStatement(sql,resultSetType,resultSetConcurrency);
}
@Override
public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
return con.prepareCall(sql,resultSetType,resultSetConcurrency);
}
@Override
public Map<String, Class<?>> getTypeMap() throws SQLException {
return con.getTypeMap();
}
@Override
public void setTypeMap(Map<String, Class<?>> map) throws SQLException {
con.setTypeMap(map);
}
@Override
public void setHoldability(int holdability) throws SQLException {
con.setHoldability(holdability);
}
@Override
public int getHoldability() throws SQLException {
return con.getHoldability();
}
@Override
public Savepoint setSavepoint() throws SQLException {
return con.setSavepoint();
}
@Override
public Savepoint setSavepoint(String name) throws SQLException {
return con.setSavepoint(name);
}
@Override
public void rollback(Savepoint savepoint) throws SQLException {
con.rollback(savepoint);
}
@Override
public void releaseSavepoint(Savepoint savepoint) throws SQLException {
con.releaseSavepoint(savepoint);
}
@Override
public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
return con.createStatement(resultSetType,resultSetConcurrency,resultSetHoldability);
}
@Override
public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
return con.prepareStatement(sql,resultSetType,resultSetConcurrency,resultSetHoldability);
}
@Override
public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
return con.prepareCall(sql,resultSetType,resultSetConcurrency,resultSetHoldability);
}
@Override
public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
return con.prepareStatement(sql,autoGeneratedKeys);
}
@Override
public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
return con.prepareStatement(sql,columnIndexes);
}
@Override
public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
return con.prepareStatement(sql,columnNames);
}
@Override
public Clob createClob() throws SQLException {
return con.createClob();
}
@Override
public Blob createBlob() throws SQLException {
return con.createBlob();
}
@Override
public NClob createNClob() throws SQLException {
return con.createNClob();
}
@Override
public SQLXML createSQLXML() throws SQLException {
return con.createSQLXML();
}
@Override
public boolean isValid(int timeout) throws SQLException {
return con.isValid(timeout);
}
@Override
public void setClientInfo(String name, String value) throws SQLClientInfoException {
con.setClientInfo(name,value);
}
@Override
public void setClientInfo(Properties properties) throws SQLClientInfoException {
con.setClientInfo(properties);
}
@Override
public String getClientInfo(String name) throws SQLException {
return con.getClientInfo(name);
}
@Override
public Properties getClientInfo() throws SQLException {
return con.getClientInfo();
}
@Override
public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
return con.createArrayOf(typeName,elements);
}
@Override
public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
return con.createStruct(typeName,attributes);
}
@Override
public void setSchema(String schema) throws SQLException {
con.setSchema(schema);
}
@Override
public String getSchema() throws SQLException {
return con.getSchema();
}
@Override
public void abort(Executor executor) throws SQLException {
con.abort(executor);
}
@Override
public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {
con.setNetworkTimeout(executor,milliseconds);
}
@Override
public int getNetworkTimeout() throws SQLException {
return con.getNetworkTimeout();
}
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
return con.unwrap(iface);
}
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
return con.isWrapperFor(iface);
}
}
– 自定义连接类
/*
自定义Connection连接类。通过适配器设计模式。完成close()方法的重写
1.定义一个类，继承适配器父类
2.定义Connection连接对象和连接池容器对象的变量
3.提供有参构造方法，接收连接对象和连接池对象，对变量赋值
4.在close()方法中，完成连接的归还
*/
public class MyConnection3 extends MyAdapter {
//2.定义Connection连接对象和连接池容器对象的变量
private Connection con;
private List<Connection> pool;
//3.提供有参构造方法，接收连接对象和连接池对象，对变量赋值
public MyConnection3(Connection con,List<Connection> pool) {
super(con); // 将接收的数据库连接对象给适配器父类传递
this.con = con;
this.pool = pool;
}
//4.在close()方法中，完成连接的归还
@Override
public void close() throws SQLException {
pool.add(con);
}
}
– 自定义连接池类
public class MyDataSource implements DataSource{
//定义集合容器，用于保存多个数据库连接对象
private static List<Connection> pool = Collections.synchronizedList(new ArrayList<Connection>());
//静态代码块，生成10个数据库连接保存到集合中
static {
for (int i = 0; i < 10; i++) {
Connection con = JDBCUtils.getConnection();
pool.add(con);
}
}
//返回连接池的大小
public int getSize() {
return pool.size();
}
//从池中返回一个数据库连接
@Override
public Connection getConnection() {
if(pool.size() > 0) {
//从池中获取数据库连接
Connection con = pool.remove(0);
//通过自定义连接对象进行包装
//MyConnection2 mycon = new MyConnection2(con,pool);
MyConnection3 mycon = new MyConnection3(con,pool);
//返回包装后的连接对象
return mycon;
}else {
throw new RuntimeException("连接数量已用尽");
}
}
}
• 动态代理
– 经过我们适配器模式的改进，自定义连接类中的方法已经很简洁了。剩余所有的方法已经抽取到了适配器类中。但是适配器这个类还是我们自己编写的，也比较麻烦！所以可以使用动态代理的方式来改进。
– 自定义数据库连接池类
public class MyDataSource implements DataSource{
//定义集合容器，用于保存多个数据库连接对象
private static List<Connection> pool = Collections.synchronizedList(new ArrayList<Connection>());
//静态代码块，生成10个数据库连接保存到集合中
static {
for (int i = 0; i < 10; i++) {
Connection con = JDBCUtils.getConnection();
pool.add(con);
}
}
//返回连接池的大小
public int getSize() {
return pool.size();
}
//动态代理方式
@Override
public Connection getConnection() {
if(pool.size() > 0) {
//从池中获取数据库连接
Connection con = pool.remove(0);
Connection proxyCon = (Connection)Proxy.newProxyInstance(con.getClass().getClassLoader(), new Class[]{Connection.class}, new InvocationHandler() {
/*
执行Connection实现类所有方法都会经过invoke
如果是close方法，则将连接还回池中
如果不是，直接执行实现类的原有方法
*/
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if(method.getName().equals("close")) {
pool.add(con);
return null;
}else {
return method.invoke(con,args);
}
}
});
return proxyCon;
}else {
throw new RuntimeException("连接数量已用尽");
}
}
//从池中返回一个数据库连接
/*@Override
public Connection getConnection() {
if(pool.size() > 0) {
//从池中获取数据库连接
Connection con = pool.remove(0);
//通过自定义连接对象进行包装
//MyConnection2 mycon = new MyConnection2(con,pool);
MyConnection3 mycon = new MyConnection3(con,pool);
//返回包装后的连接对象
return mycon;
}else {
throw new RuntimeException("连接数量已用尽");
}
}*/
}
5.开源连接池的使用
• C3P0
– 基本使用
/*
使用C3P0连接池
1.导入jar包
2.导入配置文件到src目录下
3.创建c3p0连接池对象
4.获取数据库连接进行使用
*/
public class C3P0Demo1 {
public static void main(String[] args) throws Exception{
//创建c3p0连接池对象
DataSource dataSource = new ComboPooledDataSource();
//获取数据库连接进行使用
Connection con = dataSource.getConnection();
//查询全部学生信息
String sql = "SELECT * FROM student";
PreparedStatement pst = con.prepareStatement(sql);
ResultSet rs = pst.executeQuery();
while(rs.next()) {
System.out.println(rs.getInt("sid") + "\t" + rs.getString("name") + "\t" + rs.getInt("age") + "\t" + rs.getDate("birthday"));
}
//释放资源
rs.close();
pst.close();
con.close(); // 将连接对象归还池中
}
}
– 配置演示
<c3p0-config>
<!-- 使用默认的配置读取连接池对象 -->
<default-config>
<!-- 连接参数 -->
<property name="jdbcUrl">jdbc:mysql://localhost:3306/db14</property>
<property name="user">root</property>
<property name="password">123456</property>
<!-- 连接池参数 -->
<!--初始化的连接数量-->
<property name="initialPoolSize">5</property>
<!--最大连接数量-->
<property name="maxPoolSize">10</property>
<!--超时时间-->
<property name="checkoutTimeout">3000</property>
</default-config>
<named-config name="otherc3p0">
<!-- 连接参数 -->
<property name="jdbcUrl">jdbc:mysql://localhost:3306/db15</property>
<property name="user">root</property>
<property name="password">123456</property>
<!-- 连接池参数 -->
<property name="initialPoolSize">5</property>
<property name="maxPoolSize">8</property>
<property name="checkoutTimeout">1000</property>
</named-config>
</c3p0-config>
public class C3P0Demo2 {
public static void main(String[] args) throws Exception{
//创建c3p0连接池对象
DataSource dataSource = new ComboPooledDataSource();
//获取数据库连接进行使用
for(int i = 1; i <= 11; i++) {
Connection con = dataSource.getConnection();
System.out.println(i + ":" + con);
if(i == 5) {
con.close();
}
}
}
}
• Druid
– 基本使用
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/db14
username=root
password=123456
initialSize=5
maxActive=10
maxWait=3000
/*
Druid连接池
1.导入jar包
2.编写配置文件，放在src目录下
3.通过Properties集合加载配置文件
4.通过Druid连接池工厂类获取数据库连接池对象
5.获取数据库连接，进行使用
*/
public class DruidDemo1 {
public static void main(String[] args) throws Exception{
//通过Properties集合加载配置文件
InputStream is = DruidDemo1.class.getClassLoader().getResourceAsStream("druid.properties");
Properties prop = new Properties();
prop.load(is);
//通过Druid连接池工厂类获取数据库连接池对象
DataSource dataSource = DruidDataSourceFactory.createDataSource(prop);
//获取数据库连接，进行使用
Connection con = dataSource.getConnection();
//查询全部学生信息
String sql = "SELECT * FROM student";
PreparedStatement pst = con.prepareStatement(sql);
ResultSet rs = pst.executeQuery();
while(rs.next()) {
System.out.println(rs.getInt("sid") + "\t" + rs.getString("name") + "\t" + rs.getInt("age") + "\t" + rs.getDate("birthday"));
}
//释放资源
rs.close();
pst.close();
con.close(); // 将连接对象归还池中
}
}
– 抽取工具类
/*
数据库连接池工具类
*/
public class DataSourceUtils {
//1.私有构造方法
private DataSourceUtils(){}
//2.定义DataSource数据源变量
private static DataSource dataSource;
//3.提供静态代码块，完成配置文件的加载和获取连接池对象
static {
try{
//加载配置文件
InputStream is = DruidDemo1.class.getClassLoader().getResourceAsStream("druid.properties");
Properties prop = new Properties();
prop.load(is);
//获取数据库连接池对象
dataSource = DruidDataSourceFactory.createDataSource(prop);
} catch(Exception e) {
e.printStackTrace();
}
}
//4.提供获取数据库连接的方法
public static Connection getConnection() {
Connection con = null;
try {
con = dataSource.getConnection();
} catch (SQLException e) {
e.printStackTrace();
}
return con;
}
//5.提供获取数据库连接池的方法
public static DataSource getDataSource() {
return dataSource;
}
//6.提供释放资源的方法
public static void close(Connection con, Statement stat, ResultSet rs) {
if(con != null) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(stat != null) {
try {
stat.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public static void close(Connection con, Statement stat) {
close(con,stat,null);
}
}
public class DruidTest2 {
public static void main(String[] args) throws Exception{
//1.通过连接池工具类获取一个数据库连接
Connection con = DataSourceUtils.getConnection();
String sql = "SELECT * FROM student";
PreparedStatement pst = con.prepareStatement(sql);
//2.执行sql语句，接收结果集
ResultSet rs = pst.executeQuery();
//3.处理结果集
while(rs.next()) {
System.out.println(rs.getInt("sid") + "\t" + rs.getString("name") + "\t" + rs.getInt("age") + "\t" + rs.getDate("birthday"));
}
//4.释放资源
DataSourceUtils.close(con,pst,rs);
}
}
- 点赞
- 收藏
- 关注作者
评论（0）