Java开发工程师(Web方向)

期末考试

 

编程题

本编程题包含4个小题，覆盖知识点从基础的JDBC、连接池到MyBatis。

1（10分）

有一款在线教育产品“天天向上”主要实现了在手机上查看课程表的功能。该产品的后端系统有一张保存了所有客户课程信息的数据库表，表结构如下：

请使用JDBC编写一段程序，实现读取用户名为“ZhangSan”的同学的所有课程名称，输出到控制台终端。

答：

数据库：

/usr/local/mysql/bin
./mysql -u root -p
mysql> CREATE DATABASE final_assignment;
mysql> grant all privileges on final_assignment.* to matt@localhost;
mysql> quit
./mysql -u matt -p;
mysql> use final_assignment;
mysql> CREATE TABLE Enrollment (
    -> id int auto_increment primary key,
    -> UserName varchar(100) not null,
    -> courseName varchar(100) not null
    -> );
mysql> INSERT INTO Enrollment VALUES (null, "ZhangSan", "Math");
mysql> INSERT INTO Enrollment VALUES (null, "Lisi", "Math");
mysql> INSERT INTO Enrollment VALUES (null, "ZhangSan", "Graphics");

 JDBC程序：

public class curriculum {

    static final String DRIVER_NAME = "com.mysql.jdbc.Driver";
    static final String URL = "jdbc:mysql://localhost/final_assignment";
    static final String USER_NAME = "matt";
    static final String PASSWORD = "matt";
    
    public static void curriculumDataProcessing() throws ClassNotFoundException {
        Connection conn = null;
        PreparedStatement ptmt = null;
        ResultSet rs = null;
        
        String sql = "select CourseName from Enrollment where UserName = ?";
        String userName = "ZhangSan";
        
        Class.forName(DRIVER_NAME);
        
        try {
            conn = DriverManager.getConnection(URL, USER_NAME, PASSWORD);
            ptmt = conn.prepareStatement(sql);
            ptmt.setString(1, userName);
//            System.out.println(ptmt.toString());
            rs = ptmt.executeQuery();
            
            while (rs.next()) {
                System.out.println(rs.getString("courseName"));
            }
            
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if(conn!=null) conn.close();
                if(ptmt!=null) ptmt.close();
                if(rs!=null) rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws ClassNotFoundException {
        curriculumDataProcessing();
    }
}

输出：

 

 

2（10分）

使用游标方式读取题目1中所有用户的所有课程的课程名称和用户名称，输出到控制台终端。

答：

在题1的代码中修改：

static final String URL = "jdbc:mysql://localhost/final_assignment?useCursorFetch=true";

String sql = "select UserName, CourseName from Enrollment";

ptmt.setFetchSize(2);

System.out.println(rs.getString("userName") + ": " + rs.getString("courseName"));

删除ptmt.setString(1, userName);

public class CurriculumFetchQ2 {

    static final String DRIVER_NAME = "com.mysql.jdbc.Driver";
    static final String URL = "jdbc:mysql://localhost/final_assignment?useCursorFetch=true";
    static final String USER_NAME = "matt";
    static final String PASSWORD = "matt";
    
    public static void curriculumDataProcessing() throws ClassNotFoundException {
        Connection conn = null;
        PreparedStatement ptmt = null;
        ResultSet rs = null;
        
        String sql = "select UserName, CourseName from Enrollment";
        
        Class.forName(DRIVER_NAME);
        
        try {
            conn = DriverManager.getConnection(URL, USER_NAME, PASSWORD);
            ptmt = conn.prepareStatement(sql);
            ptmt.setFetchSize(2);
            rs = ptmt.executeQuery();
            
            while (rs.next()) {
                System.out.println(rs.getString("userName") + ": " + rs.getString("courseName"));
            }
            
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if(conn!=null) conn.close();
                if(ptmt!=null) ptmt.close();
                if(rs!=null) rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws ClassNotFoundException {
        curriculumDataProcessing();
    }
}

3（10分）

使用DBCP数据库连接池实现题目1中需要完成的功能。

答：

1. add external jar -> commons-dbcp2-2.1.1.jar

2. 

package com.sheng.database.finalassignment;

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

import org.apache.commons.dbcp2.BasicDataSource;

public class CurriculumDBCPQ3 {

    public static BasicDataSource ds = null;
    
    public static final String DRIVER_NAME = "com.mysql.jdbc.Driver";
    public static final String URL = "jdbc:mysql://localhost/final_assignment";
    public static final String USER_NAME = "matt";
    public static final String PASSWORD = "matt";
    
    public static void dbpoolInit() throws ClassNotFoundException {
        // initialization
        ds = new BasicDataSource();
        
        ds.setDriverClassName(DRIVER_NAME);
        ds.setUrl(URL);
        ds.setUsername(USER_NAME);
        ds.setPassword(PASSWORD);
        ds.setMaxTotal(2);
    }
    
    public static void curriculumDataProcessing() {
        Connection conn = null;
        PreparedStatement ptmt = null;
        ResultSet rs = null;
        
        String sql = "select CourseName from Enrollment where UserName = ?";
        String userName = "ZhangSan";
        
        try {
            conn = ds.getConnection();
            ptmt = conn.prepareStatement(sql);
            ptmt.setString(0, userName);
            rs = ptmt.executeQuery();
            
            while(rs.next()) {
                System.out.println(rs.getString("courseName"));
            }
        
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (conn!=null) conn.close();
                if (ptmt!=null) ptmt.close();
                if (rs!=null) rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    
    public void run() {
        long start = System.currentTimeMillis();
        while(System.currentTimeMillis() - start < 10000) {
            curriculumDataProcessing();
        }
    }
    
    public static void main (String[] args) throws ClassNotFoundException {
        dbpoolInit();
        for (int i = 0; i < 10; i++) {
            curriculumDataProcessing();
        }
    }    
}

4（10分）

由于录入课程错误，现在需要编写一段程序，实现将“ZhangSan”的“math”课程交给“LiSi”，

你需要完成将“ZhangSan”的“math”课程记录删除，然后新插入一个“LiSi”的“math”课程，且两个过程要作为一个事务执行。

答：

package com.sheng.database.finalassignment;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class CurriculumTransactionQ4 {

    static final String DRIVER_NAME = "com.mysql.jdbc.Driver";
    static final String URL = "jdbc:mysql://localhost/final_assignment";
    static final String USER_NAME = "matt";
    static final String PASSWORD = "matt";
    
    public static void updateDataInfoByTransaction () throws ClassNotFoundException {
        Connection conn = null;
        PreparedStatement ptmt1 = null;
        PreparedStatement ptmt2 = null;
        
        String sql1 = "DELETE FROM Enrollment WHERE userName=? AND courseName=?";
        String sql2 = "INSERT INTO Enrollment VALUES (null, ?, ?)";
        String userName1 = "ZhangSan";
        String userName2 = "ZhangSan";
        String courseName = "Math";
        
        Class.forName(DRIVER_NAME);
        try {
            conn = DriverManager.getConnection(URL, USER_NAME, PASSWORD);
            conn.setAutoCommit(false);
            
            ptmt1 = conn.prepareStatement(sql1);
            ptmt1.setString(1, userName1);
            ptmt1.setString(2, courseName);
            ptmt1.execute();
            
            ptmt2 = conn.prepareStatement(sql2);
            ptmt2.setString(1, userName2);
            ptmt2.setString(2, courseName);
            ptmt2.execute();
            
            conn.commit();
            
        } catch (SQLException e) {
            if(conn!=null) {
                try {
                    conn.rollback();
                } catch (SQLException e1) {
                    e1.printStackTrace();
                }
            }
            e.printStackTrace();
        } finally {
            try {
                if (conn != null) conn.close();
                if (ptmt1 != null) ptmt1.close();
                if (ptmt2 != null) ptmt2.close();
            } catch (SQLException e) { 
                e.printStackTrace();
            }
        }
    }
    
    public static void main(String[] args) throws ClassNotFoundException {
        updateDataInfoByTransaction();
    }
}

运行后的数据库表内容：