JDBC之自定义数据库资源连接池并封装到数据库工具类

2021-10-06 19:54:01

Java为连接池实现提供了一个规范(接口),规范的写法,我们需要实现DataSource接口!

1.定义数据库的资源连接池 MyDbPool

package com.scc.utils;

import javax.sql.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.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Properties;
import java.util.logging.Logger;

/**
 * scc
 */
public class MyDbPool implements DataSource {
    private static String driverClass = null;
    private static String url = null;
    private static String user = null;
    private static String password = null;

    private static List<Connection> connections;
    static {
        connections= Collections.synchronizedList(new ArrayList<>());

        try {
            //加载属性文件
            InputStream is = MyDbPool.class.getClassLoader().getResourceAsStream("db.properties");
            //创建一个集合
            Properties properties = new Properties();
            //从流中加载
            properties.load(is);
            //获取相应的属性值
            driverClass = properties.getProperty("driverClass");
            url = properties.getProperty("url");
            user = properties.getProperty("user");
            password = properties.getProperty("password");
            System.out.println(driverClass+"  "+url+"..."+user+"..."+password);
            //注册驱动
            Class.forName(driverClass);

            for (int i = 0; i < 20; i++) {
                connections.add(DriverManager.getConnection(url, user, password));
            }
            System.out.println("数据库连接池初始化完成");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    @Override
    public Connection getConnection() throws SQLException {
       synchronized (connections){
           if(connections.size()>0){
               Connection connection = connections.remove(0);
               System.out.println("使用了:"+connection.toString());
               return connection;
           }
       }
        return null;
    }

//释放资源
    public static void release(Connection conn){
        System.out.println("归还了:"+conn.toString());
        connections.add(conn);
    }

    @Override
    public Connection getConnection(String username, String password) throws SQLException {
        return null;
    }

    @Override
    public <T> T unwrap(Class<T> 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;
    }
}

2.封装DButils工具类

package com.scc.utils;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * scc

 * 1.注册驱动
 * 2.获取连接
 * 3.释放资源
 * 4.执行增删改
 * 5.查
 */
public class DBUtils {

    private static MyDbPool  mypool;

    //注册
    static {
       mypool=new MyDbPool();
    }

    //数据库连接
    public static Connection getConnection() {
        try {
            return mypool.getConnection();
        } catch (SQLException e) {
            e.printStackTrace();
            System.out.println("连接失败");
        }
        return null;
    }

    //关流
    public static void closeAll(PreparedStatement pstat, Connection conn, ResultSet res) {
        try {
            if (res != null) {
                res.close();
            }
            if (pstat != null) {
                pstat.close();
            }
            if (conn != null) {
               mypool.release(conn);//归还连接
            }
        } catch (SQLException e) {
            e.printStackTrace();
            System.out.println("没有开流，不用关");
        }
    }

    //增删改操作
    public static int executeUpdate(String sql, Object[] params) {
        Connection conn = null;
        PreparedStatement pstat = null;
        if (sql != null) {
            try {
                //获取连接
                conn = getConnection();
                //创建命令
                pstat = conn.prepareStatement(sql);
                //遍历参数并赋值
                if (params != null) {
                    for (int i = 0; i < params.length; i++) {
                        pstat.setObject(i + 1, params[i]);
                    }
                }
                //执行方法
                return pstat.executeUpdate(); //返回值为int类型
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                closeAll(pstat, conn, null);
            }
        }
        return -1;
    }
    //获取单条数据  参数可以变化
    public static <T> T findSingle(String sql, Object[] params, Class<T> clazz) {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            conn = getConnection();
            ps = conn.prepareStatement(sql);
            if (params != null) {
                for (int i = 0; i < params.length; i++) {
                    ps.setObject(i + 1, params[i]);
                }
            }
            rs = ps.executeQuery();

            T obj = clazz.newInstance();//创建实体类的实例对象

            if (rs.next()) {
                ResultSetMetaData metaData = rs.getMetaData();//获取ResultSet的返回值对象的元数据集合
                System.out.println("列数：" + metaData.getColumnCount());
                for (int i = 0; i < metaData.getColumnCount(); i++) {
                    String columnName = metaData.getColumnName(i + 1);
                    PropertyDescriptor pd = new PropertyDescriptor(columnName, clazz);//返回的是一个对象

                    System.out.println("PropertyDescriptor的对象，pd:" + pd);
                    if (pd != null) {
                        Method writeMethod = pd.getWriteMethod();
                        writeMethod.invoke(obj, rs.getObject(columnName));
                    }
                }
            }
            return obj;
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("查询异常");
        } finally {
            closeAll(ps, conn, rs);
        }

        return null;
    }

    //查找 多条数据
    public static <T> List<T> findAll(String sql, Object[] params, Class<T> clazz) {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        List<T> list = new ArrayList<>();
        try {
            conn = getConnection();
            ps = conn.prepareStatement(sql);
            if (params != null) {
                for (int i = 0; i < params.length; i++) {
                    ps.setObject(i + 1, params[i]);
                }
            }
            rs = ps.executeQuery();
//            T obj = clazz.newInstance();//这句话不能放在外面，因为要把对象的地址放到list集合里，集合里的所有数据都单独对应一个地址

            ResultSetMetaData metaData = rs.getMetaData();//这个是获取SQL语句中要查询的列名对象，放在while里面和外卖都行
            while (rs.next()) {
                T obj = clazz.newInstance();//没创建一个对象，就把相应的地址引用方法list集合里
                for (int i = 0; i < metaData.getColumnCount(); i++) {
                    String columnName = metaData.getColumnName(i + 1);
                    Object value = rs.getObject(columnName);
                    PropertyDescriptor pd = new PropertyDescriptor(columnName, clazz);
                    Method writeMethod = pd.getWriteMethod();
                    writeMethod.invoke(obj, value);
                }

                list.add(obj);
            }
            return list;
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("查询异常");
        } finally {
            closeAll(ps, conn, rs);
        }
        return null;
    }


}

3.测试类

package com.scc.demo;

import com.scc.utils.DBUtils;

import java.sql.Connection;

/**
 * scc
 */
public class PoolTest {
    public static void main(String[] args) {
        for (int i = 0; i < 20; i++) {
            Connection conn = DBUtils.getConnection();
            System.out.println("获取连接："+conn.toString());
            DBUtils.closeAll(null, conn, null);

        }
    }
}

运行结果

"C:\Program Files\Java\jdk1.8.0_152\bin\java.exe" "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA 2018.3.3\lib\idea_rt.jar=65478:D:\Program Files\JetBrains\IntelliJ IDEA 2018.3.3\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_152\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\rt.jar;E:\IdeaWorkplace\JDBC2\out\production\JDBC2;E:\IdeaWorkplace\JDBC2\lib\mysql-connector-java-5.1.41-bin.jar;E:\Software02\repository\junit\junit\4.12\junit-4.12.jar;E:\Software02\repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar" com.scc.demo.PoolTest
com.mysql.jdbc.Driver  jdbc:mysql://localhost:3306/student...root...123456
数据库连接池初始化完成
使用了:com.mysql.jdbc.JDBC4Connection@4ccabbaa
获取连接：com.mysql.jdbc.JDBC4Connection@4ccabbaa
归还了:com.mysql.jdbc.JDBC4Connection@4ccabbaa
使用了:com.mysql.jdbc.JDBC4Connection@4bf558aa
获取连接：com.mysql.jdbc.JDBC4Connection@4bf558aa
归还了:com.mysql.jdbc.JDBC4Connection@4bf558aa
使用了:com.mysql.jdbc.JDBC4Connection@2d38eb89
获取连接：com.mysql.jdbc.JDBC4Connection@2d38eb89
归还了:com.mysql.jdbc.JDBC4Connection@2d38eb89
使用了:com.mysql.jdbc.JDBC4Connection@5fa7e7ff
获取连接：com.mysql.jdbc.JDBC4Connection@5fa7e7ff
归还了:com.mysql.jdbc.JDBC4Connection@5fa7e7ff
使用了:com.mysql.jdbc.JDBC4Connection@4629104a
获取连接：com.mysql.jdbc.JDBC4Connection@4629104a
归还了:com.mysql.jdbc.JDBC4Connection@4629104a
使用了:com.mysql.jdbc.JDBC4Connection@27f8302d
获取连接：com.mysql.jdbc.JDBC4Connection@27f8302d
归还了:com.mysql.jdbc.JDBC4Connection@27f8302d
使用了:com.mysql.jdbc.JDBC4Connection@4d76f3f8
获取连接：com.mysql.jdbc.JDBC4Connection@4d76f3f8
归还了:com.mysql.jdbc.JDBC4Connection@4d76f3f8
使用了:com.mysql.jdbc.JDBC4Connection@2d8e6db6
获取连接：com.mysql.jdbc.JDBC4Connection@2d8e6db6
归还了:com.mysql.jdbc.JDBC4Connection@2d8e6db6
使用了:com.mysql.jdbc.JDBC4Connection@23ab930d
获取连接：com.mysql.jdbc.JDBC4Connection@23ab930d
归还了:com.mysql.jdbc.JDBC4Connection@23ab930d
使用了:com.mysql.jdbc.JDBC4Connection@4534b60d
获取连接：com.mysql.jdbc.JDBC4Connection@4534b60d
归还了:com.mysql.jdbc.JDBC4Connection@4534b60d
使用了:com.mysql.jdbc.JDBC4Connection@3fa77460
获取连接：com.mysql.jdbc.JDBC4Connection@3fa77460
归还了:com.mysql.jdbc.JDBC4Connection@3fa77460
使用了:com.mysql.jdbc.JDBC4Connection@619a5dff
获取连接：com.mysql.jdbc.JDBC4Connection@619a5dff
归还了:com.mysql.jdbc.JDBC4Connection@619a5dff
使用了:com.mysql.jdbc.JDBC4Connection@1ed6993a
获取连接：com.mysql.jdbc.JDBC4Connection@1ed6993a
归还了:com.mysql.jdbc.JDBC4Connection@1ed6993a
使用了:com.mysql.jdbc.JDBC4Connection@7e32c033
获取连接：com.mysql.jdbc.JDBC4Connection@7e32c033
归还了:com.mysql.jdbc.JDBC4Connection@7e32c033
使用了:com.mysql.jdbc.JDBC4Connection@7ab2bfe1
获取连接：com.mysql.jdbc.JDBC4Connection@7ab2bfe1
归还了:com.mysql.jdbc.JDBC4Connection@7ab2bfe1
使用了:com.mysql.jdbc.JDBC4Connection@497470ed
获取连接：com.mysql.jdbc.JDBC4Connection@497470ed
归还了:com.mysql.jdbc.JDBC4Connection@497470ed
使用了:com.mysql.jdbc.JDBC4Connection@63c12fb0
获取连接：com.mysql.jdbc.JDBC4Connection@63c12fb0
归还了:com.mysql.jdbc.JDBC4Connection@63c12fb0
使用了:com.mysql.jdbc.JDBC4Connection@b1a58a3
获取连接：com.mysql.jdbc.JDBC4Connection@b1a58a3
归还了:com.mysql.jdbc.JDBC4Connection@b1a58a3
使用了:com.mysql.jdbc.JDBC4Connection@6438a396
获取连接：com.mysql.jdbc.JDBC4Connection@6438a396
归还了:com.mysql.jdbc.JDBC4Connection@6438a396
使用了:com.mysql.jdbc.JDBC4Connection@e2144e4
获取连接：com.mysql.jdbc.JDBC4Connection@e2144e4
归还了:com.mysql.jdbc.JDBC4Connection@e2144e4

Process finished with exit code 0

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