最简单的数据源，数据库连接池。

数据库连接池需要满足

• javax.sql.DataSource
• 对象池，对象池实际上是java.sql.Connection的缓存池。

实现

• maven依赖
  我使用的是org.apache.commons>commons-pool2做的对象池。

      <dependency>            <groupId>org.apache.commons</groupId>            <artifactId>commons-pool2</artifactId>            <version>2.4.2</version>        </dependency>        <dependency>            <groupId>mysql</groupId>            <artifactId>mysql-connector-java</artifactId>            <version>5.1.34</version>        </dependency>

• Java代码

package org.march.dbp.pool;import org.apache.commons.pool2.impl.GenericObjectPoolConfig;public class ConnectionConfig extends GenericObjectPoolConfig {    public ConnectionConfig() {    }}package org.march.dbp.pool;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import java.sql.Connection;import java.sql.DriverManager;import org.apache.commons.pool2.BasePooledObjectFactory;import org.apache.commons.pool2.PooledObject;import org.apache.commons.pool2.impl.DefaultPooledObject;import org.march.dbp.conn.JdbcConfig;public class ConnectionFactory extends BasePooledObjectFactory<Connection> {    private static final Class<?>[] IFACES = new Class<?>[] { Connection.class };    private JdbcConfig jdbcConfig;    private ConnectionPool connectionPool;    public ConnectionFactory(JdbcConfig jdbcConfig, ConnectionPool connectionPool) {        this.jdbcConfig = jdbcConfig;        this.connectionPool = connectionPool;    }    @Override    public Connection create() throws Exception {        Connection connection = DriverManager.getConnection(jdbcConfig.getUrl(), jdbcConfig.getPassword(),                jdbcConfig.getPassword());        Connection con = (Connection) Proxy.newProxyInstance(Connection.class.getClassLoader(), IFACES,                new InvocationHandler() {                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {                        if (method.getName().equals("close")) {                            connectionPool.returnConn((Connection) proxy);                            return null;                        } else {                            return method.invoke(connection, args);                        }                    }                });        return con;    }    @Override    public PooledObject<Connection> wrap(Connection obj) {        return new DefaultPooledObject<Connection>(obj);    }}package org.march.dbp.pool;import java.sql.Connection;import org.apache.commons.pool2.impl.GenericObjectPool;import org.march.dbp.conn.JdbcConfig;public class ConnectionPool {    private GenericObjectPool<Connection> pool = null;    public static ConnectionPool build(JdbcConfig jdbcConfig) {        return new ConnectionPool(jdbcConfig);    }    private ConnectionPool(JdbcConfig jdbcConfig) {        ConnectionConfig myPoolConfig = new ConnectionConfig();        myPoolConfig.setMaxTotal(5);        pool = new GenericObjectPool<>(new ConnectionFactory(jdbcConfig, this), myPoolConfig);    }    public Connection getConn() {        try {            Connection conn = pool.borrowObject();            return conn;        } catch (Exception e) {            e.printStackTrace();            throw new RuntimeException(e);        }    }    public void returnConn(Connection conn) {        pool.returnObject(conn);    }}package org.march.dbp.conn;public class JdbcConfig {    private String url;    private String username;    private String password;    public JdbcConfig(String url, String username, String password) {        this.url = url;        this.username = username;        this.password = password;    }    public String getUrl() {        return url;    }    public void setUrl(String url) {        this.url = url;    }    public String getUsername() {        return username;    }    public void setUsername(String username) {        this.username = username;    }    public String getPassword() {        return password;    }    public void setPassword(String password) {        this.password = password;    }    @Override    public String toString() {        return url + " " + username + " " + password;    }}package org.march.dbp.ds;import java.io.PrintWriter;import java.sql.Connection;import java.sql.SQLException;import java.sql.SQLFeatureNotSupportedException;import java.util.logging.Logger;import javax.sql.DataSource;import org.march.dbp.conn.JdbcConfig;import org.march.dbp.pool.ConnectionPool;public class MarchDataSource implements DataSource {    private PrintWriter out;    private int loginTimeout;    private ConnectionPool connectionPool;    public MarchDataSource(String url, String username, String password) {        connectionPool = ConnectionPool.build(new JdbcConfig(url, username, password));    }    @Override    public PrintWriter getLogWriter() throws SQLException {        return out;    }    @Override    public void setLogWriter(PrintWriter out) throws SQLException {        this.out = out;    }    @Override    public void setLoginTimeout(int seconds) throws SQLException {        this.loginTimeout = seconds;    }    @Override    public int getLoginTimeout() throws SQLException {        return loginTimeout;    }    @Override    public Logger getParentLogger() throws SQLFeatureNotSupportedException {        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 Connection getConnection() throws SQLException {        return connectionPool.getConn();    }    @Override    public Connection getConnection(String username, String password) throws SQLException {        return null;    }}

• 测试

public class MarchDataSourceTest extends TestCase {    public MarchDataSourceTest(String testName) {        super(testName);    }    public void testApp() throws SQLException {        MarchDataSource m = new MarchDataSource("jdbc:mysql://127.0.0.1:3306/wang", "root", "root");        Connection con = m.getConnection();        System.out.println(con);        con.close();    }}

代码在 https://github.com/faicm/march/tree/master/march-dbp。我还会持续修改。