JDBC连接池的创建
数据库连接比较消耗系统资源，连接池用来分配和管理连接，从而提高数据库连接的性能。
需要连接池的场景：
当有多个用户同时访问一个数据库的时候，将会重复创建Connection对象，并且重复释放Connection对象。试想一下，如果我用完了，不直接释放，而是交给下一个人使用，这样下一个人就不需要重复创建，从而节省重复创建和释放的时间，提高了性能。
连接池实现的原理：
1、使用集合存储Connection对象
2、需要的时候，从集合中获取Connection
3、使用完毕，将Connection放回集合中。
完整代码如下：
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.DriverManager;
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;
public class JdbcPool {
private static final String DRIVER = "com.mysql.jdbc.Driver";
private static final int SIZE = 5;
private static final String RUL = "jdbc:mysql://localhost:3306/db_hunlihui?useSSL=true";
private static final String USER = "root";
private static final String PASSWORG = "123456";
private static final LinkedList LIST = new LinkedList();
static{
try {
Class.forName(DRIVER);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
/**
* 在构造方法中初始化连接池
* @throws SQLException
*/
public JdbcPool()throws SQLException {
for(int i=0;i 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 conn.isWrapperFor(iface);
}
@Override
public Statement createStatement() throws SQLException {
// TODO Auto-generated method stub
return conn.createStatement();
}
@Override
public PreparedStatement prepareStatement(String sql) throws SQLException {
// TODO Auto-generated method stub
return conn.prepareStatement(sql);
}
@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
}
/* (non-Javadoc)
* 释放到连接池
* @see java.sql.Connection#close()
*/
@Override
public void close() throws SQLException {
LIST.add(conn);
}
@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;
}
}
}
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class TestPool {
public static void main(String[] args) {
try {
JdbcPool pool = JdbcPool.newInstance();
Connection conn = pool.getConn();
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("select * from tb_hotel");
while(rs.next()){
Integer hotelId = rs.getInt("ht_id");
String hotelName = rs.getString("ht_name");
String hotelTel = rs.getString("ht_tel");
String hotelAddress = rs.getString("ht_address");
System.out.println(hotelId+"\t"+hotelName+"\t"+hotelTel+"\t"+hotelAddress);
}
rs.close();
stmt.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}