java自定义数据库连接池以及开源连接池C3p0的使用
数据库连接池
数据库连接池的基本思想就是为数据库连接建立一个“缓冲池”。预先在缓冲池中放入一定数量的连接，当需要建立数据库连接时，只需从“缓冲池”中取出一个，使用完毕之后再放回去。
数据库连接池负责分配、管理和释放数据库连接，它允许应用程序重复使用一个现有的数据库连接，而不是重新建立一个。
一开始现在内存中开辟一块空间（集合） ， 一开先往池子里面放置 多个连接对象。 后面需要连接的话，直接从池子里面去。不要去自己创建连接了。 使用完毕， 要记得归还连接。确保连接对象能循环利用。
###自定义数据库连接池
代码实现
JDBCUtils.java
package com.songdan.util;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class JDBCUtil {
static String driverClass = null;
static String url = null;
static String name = null;
static String password= null;
static{
try {
//1. 创建一个属性配置对象
Properties properties = new Properties();
InputStream is = new FileInputStream("jdbc.properties");
//使用类加载器，去读取src底下的资源文件。 后面在servlet
// InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
//导入输入流。
properties.load(is);
//读取属性
driverClass = properties.getProperty("driverClass");
url = properties.getProperty("url");
name = properties.getProperty("name");
password = properties.getProperty("password");
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 获取连接对象
* @return
*/
public static Connection getConn(){
Connection conn = null;
try {
Class.forName(driverClass);
//静态代码块 ---> 类加载了，就执行。 java.sql.DriverManager.registerDriver(new Driver());
//DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//DriverManager.getConnection("jdbc:mysql://localhost/test?user=monty&password=greatsqldb");
//2. 建立连接 参数一： 协议 + 访问的数据库 ， 参数二： 用户名 ， 参数三： 密码。
conn = DriverManager.getConnection(url, name, password);
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}
/**
* 释放资源
* @param conn
* @param st
* @param rs
*/
public static void release(Connection conn , Statement st , ResultSet rs){
closeRs(rs);
closeSt(st);
closeConn(conn);
}
public static void release(Connection conn , Statement st ){
closeSt(st);
closeConn(conn);
}
private static void closeRs(ResultSet rs){
try {
if(rs != null){
rs.close();
}
} catch (SQLException e) {
e.printStackTrace();
}finally{
rs = null;
}
}
private static void closeSt(Statement st){
try {
if(st != null){
st.close();
}
} catch (SQLException e) {
e.printStackTrace();
}finally{
st = null;
}
}
private static void closeConn(Connection conn){
try {
if(conn != null){
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}finally{
conn = null;
}
}
}
MydataSource.java
package com.songdan.util;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import javax.sql.DataSource;
/**
* 这是一个数据库连接池
* 一开始先往池子里放10个连接
*
* 1.开始创建10个连接
*
* 2.来的程序通过getConnection获取连接
*
* 3.用完之后，使用addBack，归还连接
*
* 4.扩容
* */
public class MyDataSource implements DataSource{
List list = new ArrayList();
public MyDataSource(){
for (int i = 0; i < 10; i++) {
Connection conn = JDBCUtil.getConn();
list.add(conn);
}
}
//该连接池对外公布的获取连接的方法
@Override
public Connection getConnection() throws SQLException {
// TODO Auto-generated method stub
//获取连接的时候，先看看是否有连接
if(list.size() == 0){
for (int i = 0; i < 10; i++) {
Connection conn = JDBCUtil.getConn();
list.add(conn);
}
}
//reomove(0)移出第一个
Connection conn = list.remove(0);
return conn;
}
//用完之后记得归还
public void addBack(Connection conn){
list.add(conn);
}
@Override
public Connection getConnection(String username, String password)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PrintWriter getLogWriter() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public int getLoginTimeout() throws SQLException {
// TODO Auto-generated method stub
return 0;
}
@Override
public void setLogWriter(PrintWriter out) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void setLoginTimeout(int seconds) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public boolean isWrapperFor(Class iface) throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public T unwrap(Class iface) throws SQLException {
// TODO Auto-generated method stub
return null;
}
}
TestPool.java
package com.songdan.test;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.junit.Test;
import com.songdan.util.JDBCUtil;
import com.songdan.util.MyDataSource;
public class TestPool {
@Test
public void testPool() {
MyDataSource dataSource = new MyDataSource();
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
conn = dataSource.getConnection();
String sql = "select * from ";
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
ps.close();
rs.close();
} catch (SQLException e) {
e.printStackTrace();
} finally{
dataSource.addBack(conn);
}
}
}
}
出现的问题：
1.需要额外记住 addBack方法
2.单例。
3.无法面向接口编程。
UserDao dao = new UserDaoImpl(); dao.insert();
DataSource dataSource = new MyDataSource();
因为接口里面没有定义addBack方法。
4.怎么解决? 以addBack 为切入点。
###解决自定义数据库连接池出现的问题。
由于多了一个addBack 方法，所以使用这个连接池的地方，需要额外记住这个方法，并且还不能面向接口编程。
我们打算修改接口中的那个close方法。 原来的Connection对象的close方法，是真的关闭连接。 打算修改这个close方法，以后在调用close， 并不是真的关闭，而是归还连接对象。
###如何扩展某一个方法?
原有的方法逻辑，不是我们想要的。 想修改自己的逻辑
直接改源码 无法实现。
继承， 必须得知道这个接口的具体实现是谁。
使用装饰者模式。
代码实现
MydataSource.java
package com.songdan.util;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import javax.sql.DataSource;
/**
* 这是一个数据库连接池
* 一开始先往池子里放10个连接
*
* 1.开始创建10个连接
*
* 2.来的程序通过getConnection获取连接
*
* 3.用完之后，使用addBack，归还连接
*
* 4.扩容
* */
public class MyDataSource implements DataSource{
List list = new ArrayList();
public MyDataSource(){
for (int i = 0; i < 10; i++) {
Connection conn = JDBCUtil.getConn();
list.add(conn);
}
}
//该连接池对外公布的获取连接的方法
@Override
public Connection getConnection() throws SQLException {
// TODO Auto-generated method stub
//获取连接的时候，先看看是否有连接
if(list.size() == 0){
for (int i = 0; i < 10; i++) {
Connection conn = JDBCUtil.getConn();
list.add(conn);
}
}
//reomove(0)移出第一个
Connection conn = list.remove(0);
//在把这个对象抛出去的时候，先对这个对象进行包装
Connection connection = new ConnectionWraper(conn, list);
return connection;
}
//用完之后记得归还
public void addBack(Connection conn){
list.add(conn);
}
@Override
public Connection getConnection(String username, String password)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PrintWriter getLogWriter() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public int getLoginTimeout() throws SQLException {
// TODO Auto-generated method stub
return 0;
}
@Override
public void setLogWriter(PrintWriter out) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void setLoginTimeout(int seconds) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public boolean isWrapperFor(Class iface) throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public T unwrap(Class iface) throws SQLException {
// TODO Auto-generated method stub
return null;
}
}
ConnectionWraper.java
package com.songdan.util;
import java.sql.Array;
import java.sql.Blob;
import java.sql.CallableStatement;
import java.sql.Clob;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.NClob;
import java.sql.PreparedStatement;
import java.sql.SQLClientInfoException;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.SQLXML;
import java.sql.Savepoint;
import java.sql.Statement;
import java.sql.Struct;
import java.util.List;
import java.util.Map;
import java.util.Properties;
public class ConnectionWraper implements Connection{
Connection conn = null;
List list ;
public ConnectionWraper(Connection connection,List list) {
// TODO Auto-generated constructor stub
super();
this.conn = connection;
this.list = list;
}
@Override
public void close() throws SQLException {
//conn.close();
System.out.println("归还连接之前，池子有"+list.size()+"个连接");
list.add(conn);
System.out.println("归还连接之后，池子有"+list.size()+"个连接");
}
@Override
public PreparedStatement prepareStatement(String sql) throws SQLException {
return conn.prepareStatement(sql);
}
public void setConn(Connection conn) {
this.conn = conn;
}
@Override
public void clearWarnings() throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void commit() throws SQLException {
// TODO Auto-generated method stub
}
@Override
public Array createArrayOf(String typeName, Object[] elements)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Blob createBlob() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Clob createClob() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public NClob createNClob() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public SQLXML createSQLXML() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Statement createStatement() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Statement createStatement(int resultSetType, int resultSetConcurrency)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Statement createStatement(int resultSetType,
int resultSetConcurrency, int resultSetHoldability)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Struct createStruct(String typeName, Object[] attributes)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public boolean getAutoCommit() throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public String getCatalog() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Properties getClientInfo() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public String getClientInfo(String name) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public int getHoldability() throws SQLException {
// TODO Auto-generated method stub
return 0;
}
@Override
public DatabaseMetaData getMetaData() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public int getTransactionIsolation() throws SQLException {
// TODO Auto-generated method stub
return 0;
}
@Override
public Map> getTypeMap() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public SQLWarning getWarnings() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public boolean isClosed() throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public boolean isReadOnly() throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public boolean isValid(int timeout) throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public String nativeSQL(String sql) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public CallableStatement prepareCall(String sql) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public CallableStatement prepareCall(String sql, int resultSetType,
int resultSetConcurrency) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public CallableStatement prepareCall(String sql, int resultSetType,
int resultSetConcurrency, int resultSetHoldability)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PreparedStatement prepareStatement(String sql, int[] columnIndexes)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PreparedStatement prepareStatement(String sql, String[] columnNames)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PreparedStatement prepareStatement(String sql, int resultSetType,
int resultSetConcurrency) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PreparedStatement prepareStatement(String sql, int resultSetType,
int resultSetConcurrency, int resultSetHoldability)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void releaseSavepoint(Savepoint savepoint) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void rollback() throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void rollback(Savepoint savepoint) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void setAutoCommit(boolean autoCommit) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void setCatalog(String catalog) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void setClientInfo(Properties properties)
throws SQLClientInfoException {
// TODO Auto-generated method stub
}
@Override
public void setClientInfo(String name, String value)
throws SQLClientInfoException {
// TODO Auto-generated method stub
}
@Override
public void setHoldability(int holdability) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void setReadOnly(boolean readOnly) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public Savepoint setSavepoint() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Savepoint setSavepoint(String name) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void setTransactionIsolation(int level) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void setTypeMap(Map> map) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public boolean isWrapperFor(Class iface) throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public T unwrap(Class iface) throws SQLException {
// TODO Auto-generated method stub
return null;
}
}
JDBCUtil.java 与上面一致不变
TestPool.java 与·上面一致不变
使用c3p0连接池
src1下创建c3p0-config.xml
com.mysql.jdbc.Driver
jdbc:mysql://localhost/day06
root
123456
10
30
100
10
200
50
100
50
1000
0
5
1
1
1
5
50
TestC3p0Demo02.java
package com.songdan.c3p0;
import java.sql.Connection;
import java.sql.PreparedStatement;
import org.junit.Test;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import com.songdan.util.JDBCUtil02;
public class TestC3p0Demo02 {
@Test
public void TestC3p0(){
Connection conn = null;
PreparedStatement ps = null;
try {
//得到连接
conn = JDBCUtil02.getConnection();
String sql = "insert into account values(null,?,?)";
ps = conn.prepareStatement(sql);
ps.setString(1, "王五");
ps.setInt(2, 1000);
ps.executeUpdate();
} catch (Exception e) {
JDBCUtil02.release(conn, ps);
}
}
}
JDBCUtil02.java
package com.songdan.util;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
import com.mchange.v2.c3p0.ComboPooledDataSource;
public class JDBCUtil02 {
static ComboPooledDataSource dataSource = null;
static{
dataSource = new ComboPooledDataSource();
}
/**
* 获取连接对象
* @return
* @throws SQLException
*/
public static Connection getConn() throws SQLException{
return dataSource.getConnection();
}
/**
* 释放资源
* @param conn
* @param st
* @param rs
*/
public static void release(Connection conn , Statement st , ResultSet rs){
closeRs(rs);
closeSt(st);
closeConn(conn);
}
public static void release(Connection conn , Statement st ){
closeSt(st);
closeConn(conn);
}
private static void closeRs(ResultSet rs){
try {
if(rs != null){
rs.close();
}
} catch (SQLException e) {
e.printStackTrace();
}finally{
rs = null;
}
}
private static void closeSt(Statement st){
try {
if(st != null){
st.close();
}
} catch (SQLException e) {
e.printStackTrace();
}finally{
st = null;
}
}
private static void closeConn(Connection conn){
try {
if(conn != null){
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}finally{
conn = null;
}
}
}
使用开源的DBUtils
什么是DBUtils
Commons DbUtils是Apache组织提供的一个对JDBC进行简单封装的开源工具类库，使用它能够简化JDBC应用程序的开发，同时也不会影响程序的性能
怎么用
1. 导入jar包 commons-dbutils-1.4.jar
语法
增删改
ComboPooledDataSource dataSource = new ComboPooledDataSource();
//dbutils 知识帮我们简化CRUD的代码，但是创建连接的工作，不在它的工作范围
QueryRunner queryRunner = new QueryRunner(dataSource);
//插入
queryRunner.update("insert into account values (null,?,?)","aa",1000);
//删除
queryRunner.update("delete from account where id = ?",5);
//更新
queryRunner.update("update account set money = ? where id = ?",555,3);查询
1.直接new接口的匿名实现类
QueryRunner queryRunner = new QueryRunner(new ComboPooledDataSource());
Account account = queryRunner.query("select * from account where id = ?", new ResultSetHandler(){
@Override
public Account handle(ResultSet rs) throws SQLException {
Account account = new Account();
while(rs.next()){
String name = rs.getString("name");
int money = rs.getInt("money");
account.setName(name);
account.setMoney(money);
}
return account;
}
}, 6);
System.out.println(account.toString()); 2.直接使用框架已经写好的实现类。
查询单个对象
QueryRunner queryRunner = new QueryRunner(new ComboPooledDataSource());
//查询单个对象
Account account = queryRunner.query("select * from account where id = ?", new BeanHandler(Account.class), 8);
查询多个对象
QueryRunner queryRunner = new QueryRunner(new ComboPooledDataSource());
List list = queryRunner.query("select * from account ", new BeanListHandler(Account.class));