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JDBC|连接池-归还连接详解(上)
java数据库jdbc开发语言
- 目录
归还数据库连接的方式
继承方式归还数据库连接的思想
继承方式归还数据库连接的实现步骤
继承方式归还数据库连接存在的问题
装饰设计模式归还数据库连接的思想
装饰设计模式归还数据库连接的实现步骤
装饰设计模式归还数据库连接存在的问题
装饰设计模式归还实例演示
【JDBC|连接池-归还连接详解(上)】
- 归还数据库连接的方式
- 继承方式
- 装饰设计模式
- 适配器设计模式
- 动态代理方式
- 继承方式归还数据库连接的思想
- 通过打印连接对象，发现DriverManager获取的连接实现类是JDBC4Connection
- 那我们就可以自定义一个类，继承JDBC4Connection这个类，重写close()方法，完成连接对象的归还
- 继承方式归还数据库连接的实现步骤
- 1.定义一个类，继承JDBC4Connection
- 2.定义Connection连接对象和连接池容器对象的成员变量
- 3.通过有参构造方法完成对成员变量的赋值
- 4.重写close方法，将连接对象添加到池中
- 继承方式归还数据库连接存在的问题
- 通过查看JDBC工具类获取连接的方法发现
- 我们虽然自定义了一个子类，完成了归还连接操作
- 但是DriverManager获取的还是JDBC4Connection这个对象，并不是我们的子类对象
- 而我们又不能整体去修改驱动包中类的功能，所以继承这种方式行不通
- 装饰设计模式归还数据库连接的思想
- 我们可以自定义一个类，实现Connection接口
- 这样就具备了和JDBC4Connection相同的行为了
- 重写close()方法，完成连接的归还
- 其余的功能还调用mysql驱动包实现类原有的方法即可
- 装饰设计模式归还数据库连接的实现步骤
- 1.定义一个类，实现Connection接口
- 2.定义Connection连接对象和连接池容器对象的成员变量
- 3.通过有参构造方法完成对成员变量的赋值
- 4.重写close()方法，将连接对象添加到池中
- 5.剩余方法，只需要调用mysql驱动包的连接对象完成即可
- 6.在自定义连接池中，将获取的连接对象通过自定义连接对象进行包装
- 装饰设计模式归还数据库连接存在的问题
- 实现Connection接口后
- 有大量的方法需要在自定义类中重写
- 装饰设计模式归还实例演示
文章图片
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package demo02.myDataSourse;
import java.sql.*;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.Executor;
//1.定义一个类，实现Connection接口
public class demomyConnection implements Connection {
//2.定义连接对象和连接池容器对象的成员变量
private Connection con;
private List pool;
//3.通过有参构造方法为成员变量赋值
public demomyConnection(Connection con, List pool) {
this.con = con;
this.pool = pool;
}
//4.重写close方法，完成归还连接
@Override
public void close() throws SQLException {
pool.add(con);
}
//5.剩余方法，还是调用原有的连接对象中的功能即可
@Override
public Statement createStatement() throws SQLException {
return con.createStatement();
}@Override
public PreparedStatement prepareStatement(String sql) throws SQLException {
return con.prepareStatement(sql);
}@Override
public CallableStatement prepareCall(String sql) throws SQLException {
return con.prepareCall(sql);
}@Override
public String nativeSQL(String sql) throws SQLException {
return con.nativeSQL(sql);
}@Override
public void setAutoCommit(boolean autoCommit) throws SQLException {
con.setAutoCommit(autoCommit);
}@Override
public boolean getAutoCommit() throws SQLException {
return con.getAutoCommit();
}@Override
public void commit() throws SQLException {
con.commit();
}@Override
public void rollback() throws SQLException {
con.rollback();
}@Override
public boolean isClosed() throws SQLException {
return con.isClosed();
}@Override
public DatabaseMetaData getMetaData() throws SQLException {
return con.getMetaData();
}@Override
public void setReadOnly(boolean readOnly) throws SQLException {
con.setReadOnly(readOnly);
}@Override
public boolean isReadOnly() throws SQLException {
return con.isReadOnly();
}@Override
public void setCatalog(String catalog) throws SQLException {
con.setCatalog(catalog);
}@Override
public String getCatalog() throws SQLException {
return con.getCatalog();
}@Override
public void setTransactionIsolation(int level) throws SQLException {
con.setTransactionIsolation(level);
}@Override
public int getTransactionIsolation() throws SQLException {
return con.getTransactionIsolation();
}@Override
public SQLWarning getWarnings() throws SQLException {
return con.getWarnings();
}@Override
public void clearWarnings() throws SQLException {
con.clearWarnings();
}@Override
public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
return con.createStatement(resultSetType,resultSetConcurrency);
}@Override
public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
return con.prepareStatement(sql,resultSetType,resultSetConcurrency);
}@Override
public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
return con.prepareCall(sql,resultSetType,resultSetConcurrency);
}@Override
public Map> getTypeMap() throws SQLException {
return con.getTypeMap();
}@Override
public void setTypeMap(Map> map) throws SQLException {
con.setTypeMap(map);
}@Override
public void setHoldability(int holdability) throws SQLException {
con.setHoldability(holdability);
}@Override
public int getHoldability() throws SQLException {
return con.getHoldability();
}@Override
public Savepoint setSavepoint() throws SQLException {
return con.setSavepoint();
}@Override
public Savepoint setSavepoint(String name) throws SQLException {
return con.setSavepoint(name);
}@Override
public void rollback(Savepoint savepoint) throws SQLException {
con.rollback(savepoint);
}@Override
public void releaseSavepoint(Savepoint savepoint) throws SQLException {
con.releaseSavepoint(savepoint);
}@Override
public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
return con.createStatement(resultSetType,resultSetConcurrency,resultSetHoldability);
}@Override
public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
return con.prepareStatement(sql,resultSetType,resultSetConcurrency,resultSetHoldability);
}@Override
public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
return con.prepareCall(sql,resultSetType,resultSetConcurrency,resultSetHoldability);
}@Override
public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
return con.prepareStatement(sql,autoGeneratedKeys);
}@Override
public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
return con.prepareStatement(sql,columnIndexes);
}@Override
public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
return con.prepareStatement(sql,columnNames);
}@Override
public Clob createClob() throws SQLException {
return con.createClob();
}@Override
public Blob createBlob() throws SQLException {
return con.createBlob();
}@Override
public NClob createNClob() throws SQLException {
return con.createNClob();
}@Override
public SQLXML createSQLXML() throws SQLException {
return con.createSQLXML();
}@Override
public boolean isValid(int timeout) throws SQLException {
return con.isValid(timeout);
}@Override
public void setClientInfo(String name, String value) throws SQLClientInfoException {
con.setClientInfo(name,value);
}@Override
public void setClientInfo(Properties properties) throws SQLClientInfoException {
con.setClientInfo(properties);
}@Override
public String getClientInfo(String name) throws SQLException {
return con.getClientInfo(name);
}@Override
public Properties getClientInfo() throws SQLException {
return con.getClientInfo();
}@Override
public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
return con.createArrayOf(typeName,elements);
}@Override
public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
return con.createStruct(typeName,attributes);
}@Override
public void setSchema(String schema) throws SQLException {
con.setSchema(schema);
}@Override
public String getSchema() throws SQLException {
return con.getSchema();
}@Override
public void abort(Executor executor) throws SQLException {
con.abort(executor);
}@Override
public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {
con.setNetworkTimeout(executor,milliseconds);
}@Override
public int getNetworkTimeout() throws SQLException {
return con.getNetworkTimeout();
}@Override
public T unwrap(Class iface) throws SQLException {
return con.unwrap(iface);
}@Override
public boolean isWrapperFor(Class iface) throws SQLException {
return con.isWrapperFor(iface);
}
}
文章图片
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package demo02.myDataSourse;
import demo02.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.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.logging.Logger;
//自定义数据库连接池
public class demoDataSourse implements DataSource{
//1.准备容器，用于保存多个连接对象
private static List pool = Collections.synchronizedList(new ArrayList<>());
//2.定义静态代码块，通过工具类获取10个连接对象
static{
for(int i=1;
i<=10;
i++){
Connection con = JDBCUtils.getConnection();
pool.add(con);
}
}
//3.重写getConnection(),用于获取一个连接对象
@Override
public Connection getConnection() throws SQLException {
if(pool.size()>0){
Connection con = pool.remove(0);
//通过自定义的连接对象，对原有的连接对象进行包装
demomyConnection mycon = new demomyConnection(con,pool);
return mycon;
}else{
throw new RuntimeException("连接数量已用尽");
}
}
//4.定义getSize方法，获取连接池容器的大小
public int getSize(){
return pool.size();
}
@Override
public Connection getConnection(String username, String password) throws SQLException {
return null;
}@Override
public T unwrap(Class 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;
}
}
文章图片
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package demo02.myDataSourse;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
public class demoDataSourseTest {
public static void main(String[] args) throws Exception {
//1.创建连接池对象
demoDataSourse dataSourse = new demoDataSourse();
System.out.println("使用之前的数量" + dataSourse.getSize());
//2.通过连接池对象获取连接对象
Connection con = dataSourse.getConnection();
//3.查询学生表的全部信息
String sql = "SELECT * FROM student";
PreparedStatement pst = con.prepareStatement(sql);
//4.执行sql语句,接收结果集
ResultSet rs = pst.executeQuery();
//5.处理结果集
while(rs.next()){
System.out.println(rs.getInt("sid")+"\t"+rs.getString("name")+"\t"+rs.getInt("age")+"\t"+rs.getDate("birthday"));
}
//6.释放资源
rs.close();
pst.close();
con.close();
//用完以后，进行归还System.out.println("使用之后的数量" + dataSourse.getSize());
}
}
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