JDBC连接池：自定义连接池：方法增强（使用装饰者设计模式增强）（接上篇）
为什么需要增强？
自定义连接池中存在严重的问题，用户调用getConnection()获得连接后，必须使用release()方法进行连接的归还，如果用户调用conn.close()将连接真正的释放，连接池中出现无连接可用。
因此就希望，即使调用了close()方法，连接仍归还给连接池。close()方法原有功能释放资源时，期望功能：将当前及连接归还连接池。说明close()方法没有我们希望的功能，因此需要对close()方法进行增强，从而实现将连接归还给连接池的功能。
都有哪些方法增强的方法？
选用装饰者设计模式进行close()方法的增强：
代码实现：
使用装饰者设计模式增强close（）方法 ：MyConnection
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 pool;
//2.编写一个构造方法(参数使用了面向对象的多态特性)
public MyConnection(Connection conn,LinkedList 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 {
// TODO Auto-generated method stub
return conn.prepareStatement(sql);
}
@Override
public T unwrap(Class 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> getTypeMap() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void setTypeMap(Map> 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;
}
}
自定义连接池代码（close（）增强）：MyDataSource1
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 pool = new LinkedList();
//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 unwrap(Class 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;
}
}
JDBC连接和释放资源代码：JDBCUtils_V3
package cn.itheima.jdbc.utils;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
/**
* 提供获取连接和释放资源的 方法
*
*/
public class JDBCUtils_V3 {
/**
* 获取连接方法
*
* @return
*/
public static Connection getConnection() {
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/web08", "root", "ao1221");
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}
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();
}
}
}
}
properties配置文件
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/web08?useUnicode=true&characterEncoding=utf8
username=root
password=ao1221测试代码：
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);
}
}
}
运行结果：
