1、java自定义连接池
1.1连接池的概念：
实际开发中"获取连接"或“释放资源”是非常消耗系统资源的两个过程，为了姐姐此类性能问题，通常情况我们采用连接池技术来贡献连接Connection
用池来管理Connection，这样可以重复使用Connection，有了池，所以我们就不用自己来创建Connection，而是通过池来获取Connection对象，当使用完Connection后，调用Connection的close()方法也不会真的关闭Connection,而是把Connection“归还”给池，池也就可以再利用这个Connection对象啦
1.2 自定义连接池需要如下步骤
1.2.1 创建连接池实现（数据源），并实现接口javax.sql.DataSource.简化本案案例，我们可以自己提供方法，没有实现接口
1.2.2 提供一个集合，用于存放连接，因为移除/添加操作过多，所以选用LinkedList较好
1.2.3 为连接池初始化5个连接
1.2.4 程序如果需要连接，调用实现类的getConnection(),本方法姜葱连接池（容器List）获取连接，为了保证当前连接只是停工给一个线程使用，我们需要将连接先从连接池冲移除。
1.2.5 当用户使用完连接，释放资源时，不执行close()方法，而是将连接添加到连接池中
代码实现：
package com.rookie.bigdata.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; /** * @author * @date 2019/1/13 */ public class JDBCUtils { 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.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(); } } } }
package com.rookie.bigdata.datasource; import com.rookie.bigdata.utils.JDBCUtils; import javax.sql.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; /** * @author liuxili * @date 2019/1/13 */ public class MyDataSource implements DataSource { //创建一个容器，用于存放connection对象 private static LinkedList<Connection> pool = new LinkedList<>(); //初始化5个连接，放到容器中 static { for (int i = 0; i < 5; i++) { Connection connection = JDBCUtils.getConnection(); pool.add(connection); } } /** * 获取连接的方法 * * @return * @throws SQLException */ @Override public Connection getConnection() throws SQLException { //当连接池中没有连接的时候，需要创建链接 if (pool.size() == 0) { for (int i = 0; i < 5; i++) { Connection connection = JDBCUtils.getConnection(); pool.add(connection); } } //从池中获取连接 return pool.remove(0); } /** * 归还连接到连接池中 * * @param connection */ public void releaseConnetion(Connection connection) { pool.add(connection); } @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; } }
driver=com.mysql.jdbc.Driver url=jdbc:mysql://localhost:3306/web?useUnicode=true&characterEncoding=utf8 username=root password=root
测试类：
package com.rookie.bigdata.datasource; import org.junit.Test; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.SQLException; import static org.junit.Assert.*; /** * @author * @date 2019/1/13 */ public class MyDataSourceTest { @Test public void test1() throws SQLException { MyDataSource myDataSource = new MyDataSource(); Connection connection = myDataSource.getConnection(); String sql = "insert into H_USER values(?,?,?)"; PreparedStatement preparedStatement = connection.prepareStatement(sql); preparedStatement.setInt(1,1); preparedStatement.setString(2, "张三"); preparedStatement.setInt(3, 23); int rows = preparedStatement.executeUpdate(); System.out.println(rows); myDataSource.releaseConnetion(connection); } }
java自定义连接池改进
实现Connection接口
package com.rookie.bigdata.datasource; import java.sql.*; import java.util.LinkedList; import java.util.Map; import java.util.Properties; import java.util.concurrent.Executor; /** * @author * @date 2019/1/13 */ //实现一个Connection接口 public class MyConnection implements Connection { //定义一个变量 private Connection connection; private LinkedList<Connection> pool; //编写构造方法 public MyConnection(Connection connection, LinkedList<Connection> pool){ this.connection=connection; this.pool=pool; } @Override public void close() throws SQLException { pool.add(connection); } @Override public PreparedStatement prepareStatement(String sql) throws SQLException { return connection.prepareStatement(sql); } @Override public Statement createStatement() throws SQLException { return null; } @Override public CallableStatement prepareCall(String sql) throws SQLException { return null; } @Override public String nativeSQL(String sql) throws SQLException { return null; } @Override public void setAutoCommit(boolean autoCommit) throws SQLException { } @Override public boolean getAutoCommit() throws SQLException { return false; } @Override public void commit() throws SQLException { } @Override public void rollback() throws SQLException { } @Override public boolean isClosed() throws SQLException { return false; } @Override public DatabaseMetaData getMetaData() throws SQLException { return null; } @Override public void setReadOnly(boolean readOnly) throws SQLException { } @Override public boolean isReadOnly() throws SQLException { return false; } @Override public void setCatalog(String catalog) throws SQLException { } @Override public String getCatalog() throws SQLException { return null; } @Override public void setTransactionIsolation(int level) throws SQLException { } @Override public int getTransactionIsolation() throws SQLException { return 0; } @Override public SQLWarning getWarnings() throws SQLException { return null; } @Override public void clearWarnings() throws SQLException { } @Override public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException { return null; } @Override public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException { return null; } @Override public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException { return null; } @Override public Map<String, Class<?>> getTypeMap() throws SQLException { return null; } @Override public void setTypeMap(Map<String, Class<?>> map) throws SQLException { } @Override public void setHoldability(int holdability) throws SQLException { } @Override public int getHoldability() throws SQLException { return 0; } @Override public Savepoint setSavepoint() throws SQLException { return null; } @Override public Savepoint setSavepoint(String name) throws SQLException { return null; } @Override public void rollback(Savepoint savepoint) throws SQLException { } @Override public void releaseSavepoint(Savepoint savepoint) throws SQLException { } @Override public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { return null; } @Override public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { return null; } @Override public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { return null; } @Override public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException { return null; } @Override public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException { return null; } @Override public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException { return null; } @Override public Clob createClob() throws SQLException { return null; } @Override public Blob createBlob() throws SQLException { return null; } @Override public NClob createNClob() throws SQLException { return null; } @Override public SQLXML createSQLXML() throws SQLException { return null; } @Override public boolean isValid(int timeout) throws SQLException { return false; } @Override public void setClientInfo(String name, String value) throws SQLClientInfoException { } @Override public void setClientInfo(Properties properties) throws SQLClientInfoException { } @Override public String getClientInfo(String name) throws SQLException { return null; } @Override public Properties getClientInfo() throws SQLException { return null; } @Override public Array createArrayOf(String typeName, Object[] elements) throws SQLException { return null; } @Override public Struct createStruct(String typeName, Object[] attributes) throws SQLException { return null; } @Override public void setSchema(String schema) throws SQLException { } @Override public String getSchema() throws SQLException { return null; } @Override public void abort(Executor executor) throws SQLException { } @Override public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException { } @Override public int getNetworkTimeout() throws SQLException { return 0; } @Override public <T> T unwrap(Class<T> iface) throws SQLException { return null; } @Override public boolean isWrapperFor(Class<?> iface) throws SQLException { return false; } }
package com.rookie.bigdata.datasource; import com.rookie.bigdata.utils.JDBCUtils; import javax.sql.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; /** * @author liuxili * @date 2019/1/13 */ public class MyDataSource1 implements DataSource { //创建一个容器，用于存放connection对象 private static LinkedList<Connection> pool = new LinkedList<>(); //初始化5个连接，放到容器中 static { for (int i = 0; i < 5; i++) { Connection connection = JDBCUtils.getConnection(); MyConnection myConnection= new MyConnection(connection,pool); pool.add(myConnection); } } /** * 获取连接的方法 * * @return * @throws SQLException */ @Override public Connection getConnection() throws SQLException { Connection connection=null; //当连接池中没有连接的时候，需要创建链接 if (pool.size() == 0) { for (int i = 0; i < 5; i++) { connection = JDBCUtils.getConnection(); MyConnection myConnection= new MyConnection(connection,pool); pool.add(myConnection); } } //从池中获取连接 return pool.remove(0); } // /** // * 归还连接到连接池中 // * // * @param connection // */ // public void releaseConnetion(Connection connection) { // pool.add(connection); // // } @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; } }
测试代码
@Test public void test2() throws SQLException { MyDataSource1 myDataSource = new MyDataSource1(); Connection connection = myDataSource.getConnection(); String sql = "insert into H_USER values(?,?,?)"; PreparedStatement preparedStatement = connection.prepareStatement(sql); preparedStatement.setInt(1,2); preparedStatement.setString(2, "张三"); preparedStatement.setInt(3, 23); int rows = preparedStatement.executeUpdate(); System.out.println(rows); JDBCUtils.release(connection,preparedStatement,null); }
至此自定义连接池实现完毕，参考黑马程序员视频教程