Unit02： JDBC核心API

# db connection parameters
# key=value
driver=oracle.jdbc.driver.OracleDriver
url=jdbc:oracle:thin:@192.168.201.227:1521:orcl
user=openlab
pwd=open123
# datasource parameters
initSize=1
maxSize=1

package util;

import java.io.IOException;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

import org.apache.commons.dbcp.BasicDataSource;

/**
 *    1.DBUtil是DBTool的升级版
 *    2.采用了连接池来管理连接
 */
public class DBUtil {
    
    //DBCP连接池提供的实现类
    private static BasicDataSource ds;
    
    static {
        Properties p = new Properties();
        try {
            //1.读取参数
            p.load(DBUtil.class.getClassLoader()
                .getResourceAsStream("db.properties"));
            String driver = p.getProperty("driver");
            String url = p.getProperty("url");
            String user = p.getProperty("user");
            String pwd = p.getProperty("pwd");
            String initSize = p.getProperty("initSize");
            String maxSize = p.getProperty("maxSize");
            //2.创建连接池(1次)
            ds = new BasicDataSource();
            //3.向连接池设置参数
            ds.setDriverClassName(driver);
            ds.setUrl(url);
            ds.setUsername(user);
            ds.setPassword(pwd);
            ds.setInitialSize(new Integer(initSize));
            ds.setMaxActive(new Integer(maxSize));
        } catch (IOException e) {
            //异常的处理原则:
            //1.记录日志(Log4j)
            e.printStackTrace();
            //2.能解决就解决(看开发规范)
            //3.解决不了向上抛给调用者
            //具体抛出哪种类型的异常看开发规范
            throw new RuntimeException(
                "加载配置文件失败", e);
        }
    }
    
    public static Connection getConnection() 
        throws SQLException {
        return ds.getConnection();
    }
    
    /**
     * 1.目前我们使用连接都是连接池创建的
     * 2.连接池重写了连接对象内部的close()
     * 3.目前close()内部的逻辑是归还:
     *      - 清除连接对象内部包含的所有数据
     *      - 将连接对象状态设置为空闲态
     */
    public static void close(Connection conn) {
        if(conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
                throw new RuntimeException(
                    "关闭连接失败", e);
            }
        }
    }

}

package jdbc;

import java.sql.Connection;
import java.sql.Date;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import org.junit.Test;

import util.DBUtil;

public class TestDay02 {
    
    /**
     * 1.测试DBUtil
     * 2.执行DQL
     *     查询部门ID为1的员工
     */
    @Test
    public void test1() {
        //假设页面传入的查询条件是
        int deptno = 1;
        
        Connection conn = null;
        try {
            conn = DBUtil.getConnection();
            System.out.println(conn);
            Statement smt = conn.createStatement();
            String sql = 
                "select * from emps_lhh "
                + "where deptno="+deptno;
            ResultSet rs = smt.executeQuery(sql);
            while(rs.next()) {
                System.out.println(rs.getInt("empno"));
                System.out.println(rs.getString("ename"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
            //测试代码可以适当简化异常处理
        } finally {
            DBUtil.close(conn);
        }
    }

    /**
     * 演示如何使用PS执行DML
     */
    @Test
    public void test2() {
        //假设页面传入的数据是
        String ename = "曹操";
        String job = "丞相";
        int mgr = 0;
        Date hiredate = 
            Date.valueOf("2017-01-22");
        Double sal = 8000.0;
        Double comm = 9000.0;
        int deptno = 3;
        
        Connection conn = null;
        try {
            conn = DBUtil.getConnection();
            //写sql时条件用?代替
            String sql = 
                "insert into emps_lhh values("
                + "emps_seq_lhh.nextval,"
                + "?,?,?,?,?,?,?)";
            //创建PS并传入sql,PS会立刻发送此sql
            PreparedStatement ps = 
                conn.prepareStatement(sql);
            //先设置条件:给?赋值
            //ps.set类型(?的序号,?的值)
            ps.setString(1, ename);
            ps.setString(2, job);
            ps.setInt(3, mgr);
            ps.setDate(4, hiredate);
            ps.setDouble(5, sal);
            ps.setDouble(6, comm);
            ps.setInt(7, deptno);
            //发送参数,执行SQL(计划)
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn);
        }
    }
    
    /**
     * 演示如何使用PS执行DQL
     */
    @Test
    public void test3() {
        //假设页面传入的查询条件是
        int empno = 1;
        
        Connection conn = null;
        try {
            conn = DBUtil.getConnection();
            String sql = 
                "select * from emps_lhh "
                + "where empno=?";
            PreparedStatement ps = 
                conn.prepareStatement(sql);
            ps.setInt(1, empno);
            ResultSet rs = ps.executeQuery();
            if(rs.next()) {
                System.out.println(rs.getString("ename"));
                System.out.println(rs.getString("job"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn);
        }
        
    }
    
    /**
     * 使用PS执行查询语句,可以避免注入攻击
     */
    @Test
    public void test4() {
        //假设页面传入的参数是
        String user = "zhangsan";
        String pwd = "a‘ or ‘b‘=‘b";
        
        Connection conn = null;
        try {
            conn = DBUtil.getConnection();
            String sql = 
                "select * from users_lhh "
                + "where username=? "
                + "and password=?";
            PreparedStatement ps = 
                conn.prepareStatement(sql);
            ps.setString(1, user);
            ps.setString(2, pwd);
            ResultSet rs = ps.executeQuery();
            if(rs.next()) {
                System.out.println("登录成功");
            } else {
                System.out.println("账号或密码错误");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn);
        }
    }

}

package jdbc;

import java.sql.Connection;
import java.sql.Date;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;

import org.junit.Test;

import util.DBUtil;

public class TestDay03 {

    /**
     * 演示如何从ResultSetMetaData
     * 中读取结果集相关的描述信息.
     */
    @Test
    public void test1() {
        //假设页面传入的查询条件是
        int empno = 1;
        
        Connection conn = null;
        try {
            conn = DBUtil.getConnection();
            String sql = 
                "select * from emps_lhh "
                + "where empno=?";
            PreparedStatement ps = 
                conn.prepareStatement(sql);
            ps.setInt(1, empno);
            ResultSet rs = ps.executeQuery();
            //获取结果集元数据,它是一个对象,
            //内部封装了对结果集的描述信息.
            ResultSetMetaData md = rs.getMetaData();
            //多少列
            System.out.println(md.getColumnCount());
            //第1列的列名
            System.out.println(md.getColumnName(1));
            //第1列的类型的编号(常量)
            System.out.println(md.getColumnType(1));
            //第1列的类型的名称
            System.out.println(md.getColumnTypeName(1));
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn);
        }
    }

    /**
     * 模拟转账业务.
     * 
     * 假设此时用户已经登录了网银,
     * 并且已经输入了收款方账号和
     * 转账的金额,点击了转账.
     * 
     * 转账的步骤:
     * 1.验证收款方账号是否存在(查询)
     * 2.验证付款方余额是否够用(查询)
     * 3.将付款方余额-N元(修改)
     * 4.将收款方余额+N元(修改)
     */
    @Test
    public void test2() {
        //假设用户输入的信息如下
        //付款方账号
        String payId = "00001";
        //收款方账号
        String recId = "00002";
        //转账的金额
        double mny = 1000.0;
        
        //转账是一个完整的业务流程,必须保证
        //它的完整性,即该流程应处于一个事务
        //之内,所以创建一个连接.
        Connection conn = null;
        try {
            conn = DBUtil.getConnection();
            //取消自动提交事务
            conn.setAutoCommit(false);
            //1.查询收款方账号并验证
            String sql = 
                "select * from accounts_lhh "
                + "where id=?";
            PreparedStatement ps = 
                conn.prepareStatement(sql);
            ps.setString(1, recId);
            ResultSet rs = ps.executeQuery();
            if(!rs.next()) {
                throw new SQLException("收款方账号不存在");
            }
            double recMny = rs.getDouble("money");
            //2.查询付款方余额并验证
            String sql2 = 
                "select * from accounts_lhh "
                + "where id=?";
            PreparedStatement ps2 = 
                conn.prepareStatement(sql2);
            ps2.setString(1, payId);
            ResultSet rs2 = ps2.executeQuery();
            double payMny = 0.0;
            if(rs2.next()) {
                payMny = rs2.getDouble("money");
                if(payMny<mny) {
                    throw new SQLException("余额不足");
                }
            }
            //3.修改付款方余额
            String sql3 = 
                "update accounts_lhh set "
                + "money=? where id=?";
            PreparedStatement ps3 = 
                conn.prepareStatement(sql3);
            ps3.setDouble(1, payMny-mny);
            ps3.setString(2, payId);
            ps3.executeUpdate();
            
            Integer.valueOf("断电了");
            
            //4.修改收款方余额
            String sql4 =
                "update accounts_lhh set "
                + "money=? where id=?";
            PreparedStatement ps4 = 
                conn.prepareStatement(sql4);
            ps4.setDouble(1, recMny+mny);
            ps4.setString(2, recId);
            ps4.executeUpdate();
            
            //转账是一个完整的过程,只需要在
            //整个流程完成后,提交一次事务即可.
            conn.commit();
        } catch (Exception e) {
            e.printStackTrace();
            try {
                conn.rollback();
            } catch (SQLException e1) {
                e1.printStackTrace();
            }
        } finally {
            DBUtil.close(conn);
        }
    }
    
    /**
     *    批量添加员工(共108个,每批加50个)
     */
    @Test
    public void test3() {
        //这是一个完整的业务,只创建
        //1个连接,提交1次事务
        Connection conn = null;
        try {
            conn = DBUtil.getConnection();
            conn.setAutoCommit(false);
            String sql = 
                "insert into emps_lhh values("
                + "emps_seq_lhh.nextval,"
                + "?,?,?,?,?,?,?)";
            PreparedStatement ps = 
                conn.prepareStatement(sql);
            for(int i=1;i<=108;i++) {
                //每次循环都将数据暂存到ps上
                ps.setString(1, "好汉"+i);
                ps.setString(2, "打劫");
                ps.setInt(3, 0);
                ps.setDate(4, 
                    Date.valueOf("2017-01-23"));
                ps.setDouble(5, 6000.0);
                ps.setDouble(6, 4000.0);
                ps.setInt(7, 9);
                ps.addBatch();
                //每循环50次发送一次数据
                if(i%50==0) {
                    ps.executeBatch();
                    //清空ps中的数据,以便于
                    //暂存下一轮的数据
                    ps.clearBatch();
                }
            }
            //循环结束后,为了避免有零头(8),
            //再单独批量发送一次数据.由于这
            //是最后一次发送,所以不用清空ps了
            ps.executeBatch();
            conn.commit();
        } catch (SQLException e) {
            e.printStackTrace();
            try {
                conn.rollback();
            } catch (SQLException e1) {
                e1.printStackTrace();
            }
        } finally {
            DBUtil.close(conn);
        }
    }
    
    /**
     * 添加部门及员工数据
     * 添加员工时需要获取到部门的ID
     */
    @Test
    public void test4() {
        //假设页面传入的数据是
        //部门
        String dname = "财务部";
        String loc = "杭州";
        //员工
        String ename = "郭嘉";
        String job = "谋士";
        int mgr = 0;
        Date hiredate = 
            Date.valueOf("2017-01-23");
        double sal = 6000.0;
        double comm = 2000.0;
        
        Connection conn = null;
        try {
            conn = DBUtil.getConnection();
            conn.setAutoCommit(false);
            //增加部门
            String sql = 
                "insert into depts values("
                + "depts_seq.nextval,?,?)";
            //参数2是一个数组,声明需要ps记住
            //的字段的名称,ps在执行SQL时会
            //记住这些字段的值.
            PreparedStatement ps = 
                conn.prepareStatement(
                    sql, new String[]{"deptno"});
            ps.setString(1, dname);
            ps.setString(2, loc);
            ps.executeUpdate();
            //获取部门ID
            //返回的结果集中存储了一条数据,
            //该行数据包括我们让ps记录的所有字段.
            ResultSet rs = ps.getGeneratedKeys();
            System.out.println("rs"+rs);  
            //rsorg.apache.commons.dbcp.DelegatingResultSet@27efef64
            rs.next();
            //获取ps记录的字段时必须使用序号
            int deptno = rs.getInt(1);
            System.out.println("deptno"+deptno);  //deptno 4
            //增加员工
            String sql2 = 
                "insert into emps values("
                + "emps_seq.nextval,"
                + "?,?,?,?,?,?,?)";
            PreparedStatement ps2 = 
                conn.prepareStatement(sql2);
            ps2.setString(1, ename);
            ps2.setString(2, job);
            ps2.setInt(3, mgr);
            ps2.setDate(4, hiredate);
            ps2.setDouble(5, sal);
            ps2.setDouble(6, comm);
            ps2.setInt(7, deptno);
            ps2.executeUpdate();
            conn.commit();
        } catch (SQLException e) {
            e.printStackTrace();
            try {
                conn.rollback();
            } catch (SQLException e1) {
                e1.printStackTrace();
            }
        } finally {
            DBUtil.close(conn);
        }
    }
    
}