连接池

连接池

在Java中,连接池使用javax.sql.DataSource接口来表示连接池.
DataSource(数据源)和连接池(Connection Pool)是同一个.

DBCP:  Spring框架推荐的
druid: 阿里巴巴的连接池(号称Java语言中性能最好的连接池)

DBCP连接池

package me.cscar.dbcp.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;
import org.apache.commons.dbcp2.BasicDataSource;
import org.apache.commons.dbcp2.BasicDataSourceFactory;

import javax.sql.DataSource;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class JDBCutil {
    private static Properties prs = new Properties();
    private static BasicDataSource bds = null;
    //private static DataSource dsf = null;

    static {
        try {
            InputStream in = Thread.currentThread()
                    .getContextClassLoader()
                    .getResourceAsStream("db.properties");

            prs.load(in);

            Class.forName(prs.getProperty("driverClassName"));
            //在静态代码块中初始化连接池对象,连接池只需一个即可
            bds = BasicDataSourceFactory.createDataSource(prs);
            //druid连接池
            //dsf = DruidDataSourceFactory.createDataSource(prs);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() {
        try {
            Connection conn = bds.getConnection();
            //Connection conn = dsf.getConnection();
            return conn;
        } catch (Exception e) {
            e.printStackTrace();
        }
        throw new RuntimeException("数据库链接失败");
    }

    public static void close(ResultSet rs, PreparedStatement ps, Connection conn) {
        try {
            if (rs != null) {
                rs.close();
            }
            if (ps != null) {
                ps.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

druid连接池

阿里巴巴研发出来的号称Java语言领域性能最高的连接池.
wiki地址:https://github.com/alibaba/druid/wiki

使用起来,类似于DBCP连接池.
方便检测性能/状态.
支持:MySQL,Oracle,DB2,sql Server等.
支持:对配置文件的密码加密.

package me.cscar.dbcp.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;
import org.apache.commons.dbcp2.BasicDataSource;
import org.apache.commons.dbcp2.BasicDataSourceFactory;

import javax.sql.DataSource;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class JDBCutil {
    private static Properties prs = new Properties();
    //private static BasicDataSource bds = null;
    private static DataSource dsf = null;

    static {
        try {
            InputStream in = Thread.currentThread()
                    .getContextClassLoader()
                    .getResourceAsStream("db.properties");

            prs.load(in);

            Class.forName(prs.getProperty("driverClassName"));
            //在静态代码块中初始化连接池对象,连接池只需一个即可
            //bds = BasicDataSourceFactory.createDataSource(prs);
            //druid连接池
            dsf = DruidDataSourceFactory.createDataSource(prs);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() {
        try {
            //Connection conn = bds.getConnection();
            Connection conn = dsf.getConnection();
            return conn;
        } catch (Exception e) {
            e.printStackTrace();
        }
        throw new RuntimeException("数据库链接失败");
    }

    public static void close(ResultSet rs, PreparedStatement ps, Connection conn) {
        try {
            if (rs != null) {
                rs.close();
            }
            if (ps != null) {
                ps.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

代码重构

package me.cscar.dbcp.dao.impl;

import me.cscar.dbcp.dao.IemployeeDAO;
import me.cscar.dbcp.domain.Employee;
import me.cscar.dbcp.util.JDBCutil;

import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class EmployeeDAOimpl implements IemployeeDAO {

    public static EmployeeDAOimpl instance = new EmployeeDAOimpl();

    /**
     * dml操作
     *
     * @param sql
     * @param obj
     */
    @Override
    public void dml(String sql, Object... obj) {

        Connection conn = null;
        PreparedStatement ps = null;
        try {
            conn = JDBCutil.getConnection();
            ps = conn.prepareStatement(sql);
            for (int i = 0; i < obj.length; i++) {
                ps.setObject(i + 1, obj[i]);
            }
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCutil.close(null, ps, conn);
        }

    }

    /**
     * 查
     *
     * @param emp,args
     * @return
     */
    @Override
    public List<Employee> get(String sql, Object emp, Object... args) {
        List<Employee> list = new ArrayList<>();
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            conn = JDBCutil.getConnection();
            ps = conn.prepareStatement(sql);
            for (int i = 0; i < args.length; i++) {
                ps.setObject(i + 1, args[i]);
            }
            rs = ps.executeQuery();

            Class<?> clz = emp.getClass();

            while (rs.next()) {
                BeanInfo info = Introspector.getBeanInfo(clz, Object.class);
                PropertyDescriptor[] pds = info.getPropertyDescriptors();

                Object obj = clz.newInstance();

                for (PropertyDescriptor ele : pds) {
                    //id,name,salary
                    String cloumnName = ele.getName();
                    Object cloumnValue = rs.getObject(cloumnName);

                    //getter,setter
                    Method m = ele.getWriteMethod();
                    m.invoke(obj, cloumnValue);
                }

                list.add((Employee) obj);

            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCutil.close(rs, ps, conn);
        }

        return list;
    }
}