JDBC 自定义连接池

1、存放连接信息

db.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/web08?useUnicode=true&characterEncoding=utf8
username=root
password=root

2、工具类用来获取链接数据库

JDBCUtils_V3.java

package cn.itheima.jdbc.utils;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
import java.util.ResourceBundle;

/**
 * 提供获取连接和释放资源的 方法*/
public class JDBCUtils_V3 {
    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    /**
     * 静态代码块加载配置文件信息
     */
    static {
        try {
            // 1.通过当前类获取类加载器
            ClassLoader classLoader = JDBCUtils_V3.class.getClassLoader();
            // 2.通过类加载器的方法获得一个输入流
            InputStream is = classLoader.getResourceAsStream("db.properties");
            // 3.创建一个properties对象
            Properties props = new Properties();
            // 4.加载输入流
            props.load(is);
            // 5.获取相关参数的值
            driver = props.getProperty("driver");
            url = props.getProperty("url");
            username = props.getProperty("username");
            password = props.getProperty("password");
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    /**
     * 获取连接方法
     * 
     * @return
     */
    public static Connection getConnection() {
        Connection conn = null;
        try {
            Class.forName(driver);
            conn = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return conn;
    }

    /**
     * 释放资源方法
     * 
     * @param conn
     * @param pstmt
     * @param rs
     */
    public static void release(Connection conn, PreparedStatement pstmt, ResultSet rs) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (pstmt != null) {
            try {
                pstmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

    }
}

3、自定义Connection类用来自定义close()关闭连接的方法（配合连接池使用）

MyConnection.java

package cn.itheima.jdbc.DataSource;

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.LinkedList;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.Executor;

//1.实现同一个接口Connection
public class MyConnection implements Connection {
    //3.定义一个变量
    private Connection conn;
    
    private LinkedList<Connection> pool;
    
    // 2.编写一个构造方法(参数使用了面相对象的多态特性)
    public MyConnection(Connection conn,LinkedList<Connection> pool) {
        this.conn=conn;
        this.pool=pool;
    }
    
    //4.书写需要增强的方法
    @Override
    public void close() throws SQLException {
        pool.add(conn);
    }

    /**
     * 此方法必须覆盖！否则会出现空指针异常！！！
     */
    @Override
    public PreparedStatement prepareStatement(String sql) throws SQLException {
        return conn.prepareStatement(sql);
    }
    
    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public Statement createStatement() 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 String nativeSQL(String sql) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void setAutoCommit(boolean autoCommit) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public boolean getAutoCommit() throws SQLException {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public void commit() throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public void rollback() throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public boolean isClosed() throws SQLException {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public DatabaseMetaData getMetaData() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void setReadOnly(boolean readOnly) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public boolean isReadOnly() throws SQLException {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public void setCatalog(String catalog) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public String getCatalog() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void setTransactionIsolation(int level) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public int getTransactionIsolation() throws SQLException {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public SQLWarning getWarnings() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void clearWarnings() throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency) 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 CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public Map<String, Class<?>> getTypeMap() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void setTypeMap(Map<String, Class<?>> map) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public void setHoldability(int holdability) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public int getHoldability() throws SQLException {
        // TODO Auto-generated method stub
        return 0;
    }

    @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 rollback(Savepoint savepoint) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public void releaseSavepoint(Savepoint savepoint) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability)
            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 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 Clob createClob() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public Blob createBlob() 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 boolean isValid(int timeout) throws SQLException {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public void setClientInfo(String name, String value) throws SQLClientInfoException {
        // TODO Auto-generated method stub

    }

    @Override
    public void setClientInfo(Properties properties) throws SQLClientInfoException {
        // TODO Auto-generated method stub

    }

    @Override
    public String getClientInfo(String name) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public Properties getClientInfo() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public Array createArrayOf(String typeName, Object[] elements) 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 void setSchema(String schema) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public String getSchema() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void abort(Executor executor) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public int getNetworkTimeout() throws SQLException {
        // TODO Auto-generated method stub
        return 0;
    }

}

4、设置数据源连接池（数据源提供了一种简单获取数据库连接的方式，并能在内部通过一个池的机制来复用数据库连接，这样就大大减少创建数据库连接的次数，提高了系统性能。）

MyDataSource1.java

package cn.itheima.jdbc.DataSource;

import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.LinkedList;
import java.util.logging.Logger;

import javax.sql.DataSource;

import cn.itheima.jdbc.utils.JDBCUtils_V3;

public class MyDataSource1 implements DataSource{
    //1.创建1个容器用于存储Connection对象
    private static LinkedList<Connection> pool = new LinkedList<Connection>();
    
    //2.创建5个连接放到容器中去
    static{
        for (int i = 0; i < 5; i++) {
            Connection conn = JDBCUtils_V3.getConnection();
            //放入池子中connection对象已经经过改造了
            MyConnection myconn = new MyConnection(conn, pool);
            pool.add(myconn);
        }
    }
    
    /**
     * 重写获取连接的方法
     */
    @Override
    public Connection getConnection() throws SQLException {
        Connection conn = null;
        //3.使用前先判断
        if(pool.size()==0){
            //4.池子里面没有，我们再创建一些
            for (int i = 0; i < 5; i++) {
                conn = JDBCUtils_V3.getConnection();
                //放入池子中connection对象已经经过改造了
                MyConnection myconn = new MyConnection(conn, pool);
                pool.add(myconn);
            }
        }
        //5.从池子里面获取一个连接对象Connection
        conn = pool.remove(0);
        return conn;
    }

    /**
     * 归还连接对象到连接池中去
     */
    public void backConnection(Connection conn){
        pool.add(conn);
    }

    @Override
    public PrintWriter getLogWriter() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @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 int getLoginTimeout() throws SQLException {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public Logger getParentLogger() throws SQLFeatureNotSupportedException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public Connection getConnection(String username, String password) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

}

5、测试类

TestMyDataSource.java

package cn.itheima.jdbc.test;

import java.sql.Connection;
import java.sql.PreparedStatement;

import javax.sql.DataSource;

import org.junit.Test;

import cn.itheima.jdbc.DataSource.MyDataSource;
import cn.itheima.jdbc.DataSource.MyDataSource1;
import cn.itheima.jdbc.utils.JDBCUtils_V3;

public class TestMyDataSource {

    /**
     * 添加用户
     * 使用未改造过的connection
     */
    @Test
    public void testAddUser() {
        Connection conn = null;
        PreparedStatement pstmt = null;
        // 1.创建自定义连接池对象
        MyDataSource dataSource = new MyDataSource();
        try {
            // 2.从池子中获取连接
            conn = dataSource.getConnection();
            String sql = "insert into tbl_user values(null,?,?)";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, "吕布");
            pstmt.setString(2, "貂蝉");
            int rows = pstmt.executeUpdate();
            if (rows > 0) {
                System.out.println("添加成功!");
            } else {
                System.out.println("添加失败!");
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            dataSource.backConnection(conn);
        }
    }
    
    
    /**
     * 添加用户
     * 使用改造过的connection
     */
    @Test
    public void testAddUser1() {
        Connection conn = null;
        PreparedStatement pstmt = null;
        // 1.创建自定义连接池对象
        DataSource dataSource = new MyDataSource1();
        try {
            // 2.从池子中获取连接
            conn = dataSource.getConnection();
            String sql = "insert into tbl_user values(null,?,?)";
            //3.必须在自定义的connection类中重写prepareStatement(sql)方法
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, "吕布1");
            pstmt.setString(2, "貂蝉1");
            int rows = pstmt.executeUpdate();
            if (rows > 0) {
                System.out.println("添加成功!");
            } else {
                System.out.println("添加失败!");
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtils_V3.release(conn, pstmt, null);
        }
    }
}