使用包装设计模式实现自己的数据源

package com.lwh.datasource;

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

import javax.sql.DataSource;

public class MyDataSource implements DataSource{
private static String driverClassName;
private static String url;
private static String user;
private static String password;
private static LinkedList<Connection> pool = new LinkedList<>();
static{
try{
InputStream is = MyDataSource.class.getClassLoader().getResourceAsStream("db.properties");
Properties props = new Properties();
props.load(is);
driverClassName = props.getProperty("driverClassName");
url = props.getProperty("url");
user = props.getProperty("user");
password = props.getProperty("password");
Class.forName(driverClassName);

for(int i = 0; i < 10; i++){
Connection conn = DriverManager.getConnection(url, user, password);
pool.add(conn);
}

}catch(Exception e){
e.printStackTrace();
}
}
@Override
public synchronized Connection getConnection() throws SQLException {
if(pool.size() > 0){
Connection conn = pool.removeLast();
MyConnection myconn = new MyConnection(conn, pool);
return myconn;
}else{
throw new RuntimeException("服务器真忙");
}
}

@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;
}

}

package com.lwh.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;

/**
包装设计模式
a、编写一个类实现与被改写类（com.mysql.jdbc.Connection）相同的接口
b、定义一个引用，记住被改写类的实例
c、定义构造方法，传入被改写类的实例
d、对于要改写的方法，改写即可
e、对于不需要改写的方法，调用原有的对象的对应方法
*/
//改写com.mysql.jdbc.Connection中的close方法，在调用时，不是关闭连接而是返回池中
public class MyConnection implements Connection {

private Connection conn;
private LinkedList<Connection> pool;

public MyConnection(Connection conn, LinkedList<Connection> pool){
this.conn = conn;
this.pool = pool;
}

@Override
public void close() throws SQLException {
pool.addFirst(conn);
}

@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 PreparedStatement prepareStatement(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 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 g
b945
etSchema() 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;
}

}

package com.lwh.datasource;

import java.sql.Connection;
import java.sql.SQLException;

import javax.sql.DataSource;

import com.mysql.jdbc.PreparedStatement;

public class MyDataSourceClient {

private static DataSource ds = new MyDataSource();

public static void main(String[] args) {
Connection conn = null;
PreparedStatement pst = null;
try{
conn = ds.getConnection();
System.out.println(conn);
}catch(Exception e){
e.printStackTrace();
}finally{
if(pst != null){
try {
pst.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(conn != null){
try {
conn.close();//该方法应做到，不要关闭连接，而应该还回池中
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}