C3P0实现连接数据库

待我称王封你为后i 2024-04-19 10:25 0阅读 0赞

## C3P0实现连接数据库 ##

c3p0-config.xml(此文件必须放在src下,而且名字必须是这个)

<c3p0-config>
      <default-config>
    
        <property name="checkoutTimeout">30000</property>
        <property name="initialPoolSize">10</property>
        <property name="maxPoolSize">100</property>
        <property name="minPoolSize">10</property>
        <property name="maxStatements">200</property>
    
        <property name="driverClass">com.mysql.cj.jdbc.Driver</property>
        <property name="jdbcUrl">jdbc:mysql://localhost:3306/employee?characterEncoding=utf8&useSSL=false&serverTimezone=UTC&rewriteBatchedStatements=true</property>
        <property name="user">root</property>
        <property name="password">root</property>
    
      </default-config>
    </c3p0-config>

C3P0Util.java

package com.zr.utils;
    
    import java.sql.Connection;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    import com.mchange.v2.c3p0.ComboPooledDataSource;
    
    public class C3P0Util {
    	//获取数据源,只要c3p0-config.xm文件放在src下,那么会自动配置到连接池
    	//约束大于一切
    	private static ComboPooledDataSource dataSource=new ComboPooledDataSource();
    	
    	/**
    	 * 获取数据库连接
    	 * @return
    	 */
    	public static Connection getConnection() {
    		try {
    			return dataSource.getConnection();
    		} catch (SQLException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    		return null;
    	}
    	
    	/**
    	 * 关闭连接,释放资源,一定要按ResultSet,Statement,Connection前后顺序关闭
    	 * @param connection
    	 * @param statement
    	 * @param resultSet
    	 */
    	public static void close(Connection connection,Statement statement,ResultSet resultSet) {
    		if (resultSet!=null) {
    			try {
    				resultSet.close();
    			} catch (SQLException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		}
    		if (statement!=null) {
    			try {
    				statement.close();
    			} catch (SQLException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		}
    		if (connection!=null) {
    			try {
    				connection.close();//此方法会被C3P0重写,不一定真的关闭
    			} catch (SQLException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		}
    	}
    }

C3P0Demo.java

package com.zr.demo;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    
    import com.zr.utils.C3P0Util;
    
    public class C3P0Demo {
    
    	public static void main(String[] args) {
    		Connection connection = null;
    		PreparedStatement prepareStatement =null;
    		ResultSet resultSet =null;
    		//sql语句
    		String sql="select * from dept";
    		try {
    			//从C3P0连接池获取连接
    			connection = C3P0Util.getConnection();
    			//预编译sql
    			prepareStatement = connection.prepareStatement(sql);
    			//执行sql,获得数据
    			resultSet = prepareStatement.executeQuery();
    			
    			//按表格输出到控制台
    			System.out.println("deptno\tdname\t\tloc");
    			while(resultSet.next()) {
    				int deptno=resultSet.getInt(1);
    				String dname=resultSet.getString(2);
    				String loc=resultSet.getString(3);
    				System.out.println(deptno+"\t"+dname+"\t\t"+loc);
    			}
    		} catch (SQLException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}finally {
    			//关闭连接
    			C3P0Util.close(connection, prepareStatement, resultSet);
    		}
    
    	}
    
    }