JDBC学习总结(二)

1、JDBC的基本应用

1）创建数据库：

　　create database test;  

　　use test;

2）创建表：

create table student(

    id int(4) not null auto_increment,

    name varchar(20) default null,

    score int(3) default 0,

    primary key (id)

);

3）学生类：

package com.yyq;
/**
 * Created by gao on 16-4-12.
 */
public class Student {
    //学生Id
    private int id;
    //学生姓名
    private String name;
    //班级
    private String myClass;
    //分数
    private double score;
    //提供一个公共无参数的构造方法
    public Student(){
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getMyClass() {
        return myClass;
    }
    public void setMyClass(String myClass) {
        this.myClass = myClass;
    }
    public double getScore() {
        return score;
    }
    public void setScore(double score) {
        this.score = score;
    }
}

4）插入一条数据：

package com.yyq;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
/**
 * Created by gao on 16-4-12.
 */
public class DoInsert {
    private String dirver = "com.mysql.jdbc.Driver";
    private String url="jdbc:mysql://localhost:3306/test";
    private String user="root";
    private String password="123456";
    public boolean addStudent(Student stu){
        Connection conn=null;
        Statement st=null;
        String sql="INSERT INTO student(name,class,score) values('"+stu.getName()+"'," +
                "'"+stu.getMyClass()+"',"+stu.getScore()+")";
        boolean flag=false;
        try {
            Class.forName(dirver);
            conn= DriverManager.getConnection(url, user, password);
            st=conn.createStatement();
            int i=st.executeUpdate(sql);
            if(i==1){
                flag=true;
            }
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            if(st!=null){
                try {
                    st.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            if(conn!=null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
        return flag;
    }
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        DoInsert doinsert=new DoInsert();
        Student stu=new Student();
        stu.setName("xiaoming");
        stu.setMyClass("java");
        stu.setScore(98.00);
        boolean flag=doinsert.addStudent(stu);
        if(flag){
            System.out.println("成功插入一条数据!");
        }else{
            System.out.println("插入数据失败!");
        }
    }
}

5）查询数据

package com.yyq;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
/**
 * Created by gao on 16-4-12.
 */
public class DoSelect {
    //step2:提供连接数据库所需的dirver,url,user,password
    private String dirver = "com.mysql.jdbc.Driver";
    private String url="jdbc:mysql://localhost:3306/test";
    private String user="root";
    private String password="123456";
    public List<Student> findAll(){
        //声明一个局部的Connection对象
        Connection conn=null;
        //声明一个局部的Statement 对象
        Statement st=null;
        //声明一个ResultSet结果集对象
        ResultSet rs=null;
        //定义SQL语句
        String sql="select * from student";
        //保存返回结果
        List<Student> list=new ArrayList<Student>();
        try {
            //step1:加载数据库厂商提供的驱动JAR包
            Class.forName(dirver);
            //step3:通过DriverManager获取一个数据库连接对象
            conn= DriverManager.getConnection(url, user, password);
            //step4:创建一个Statement对象
            st=conn.createStatement();
            //step5:执行sql语句
            rs=st.executeQuery(sql);
            //step6:处理结果集
            while(rs.next()){
                Student stu=new Student();
                stu.setId(rs.getInt("id"));
                stu.setName(rs.getString("name"));
                stu.setMyClass(rs.getString("class"));
                stu.setScore(rs.getDouble("score"));
                list.add(stu);
            }
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            //step7:关闭连接数据库资源
            if(rs!=null){
                try {
                    rs.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            if(st!=null){
                try {
                    st.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            if(conn!=null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
        return list;
    }
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        DoSelect select=new DoSelect();
        //调用查询的方法
        List<Student> list=select.findAll();
        for(Student stu:list){
            System.out.println("Id:"+stu.getId()+"\t姓名:"+stu.getName()+"\t班级:"+stu.getMyClass()+"\t分数:"+stu.getScore());
        }
    }
}

6）使用PrepareStatement查询

    可以在查询语句中动态加入查询条件。首先，使用Connection的prepareStatement()方法建立好一个预编译的SQL语句——其中参数会变动的部分用“？”来占位。等到需要真正指定参数执行时，再使用相对应的setXXX(int parameterIndex, 值)方法，指定“？”处真正应该有的参数值。

package com.yyq;
import java.sql.*;
/**
 * Created by gao on 16-4-12.
 */
public class PreparedSelect {
    //step2:提供连接数据库所需的driver，url,user,password
    private String dirver = "com.mysql.jdbc.Driver";
    private String url="jdbc:mysql://localhost:3306/test";
    private String user="root";
    private String password="123456";
    public Student findById(int id){
        //声明一个局部的Connection对象
        Connection conn=null;
        //声明一个局部的Statement 对象
        PreparedStatement pst=null;
        //声明一个ResultSet结果集对象
        ResultSet rs=null;
        //定义SQL语句
        String sql="select * from student where id=?";
        //保存返回结果
        Student stu = null;
        try {
            //step1:加载数据库厂商提供的驱动JAR包
            Class.forName(dirver);
            //step3:通过DriverManager获取一个数据库连接对象
            conn=DriverManager.getConnection(url, user, password);
            //step4:创建一个PreparedStatement对象
            pst=conn.prepareStatement(sql);
            pst.setInt(1, id);
            //step5:执行sql语句
            rs=pst.executeQuery();
            //step6:处理结果集
            if(rs.next()){
                stu=new Student();
                stu.setId(rs.getInt("id"));
                stu.setName(rs.getString("name"));
                stu.setMyClass(rs.getString("class"));
                stu.setScore(rs.getDouble("score"));
            }
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            //step7:关闭连接数据库资源
            if(rs!=null){
                try {
                    rs.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            if(pst!=null){
                try {
                    pst.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            if(conn!=null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
        return stu;
    }
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        PreparedSelect ps=new PreparedSelect();
        //调用查询方法
        Student stu=ps.findById(12);
        System.out.println("Id:"+stu.getId()+"\t姓名:"+stu.getName()+"\t班级:"+stu.getMyClass()+"\t分数:"+stu.getScore());
    }
}

2、对JDBC操作数据库的工具类进行封装

1）对获得Connection对象进行封装

//DB_Driver
driver = com.mysql.jdbc.Driver
//DB_URL
url = jdbc:mysql://localhost:3306/test
//DB_USERNAME
username = root
//DB_PASSWORD
password = 123456

2）创建ConnectionFactory工程类，用于生产连接对象

package com.yyq.factory;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
/**
 * 数据库连接对象(Connection)工厂类
 */
public class ConnectionFactory {
    private static String DB_DRIVER;
    private static String DB_URL;
    private static String DB_USERNAME;
    private static String DB_PASSWORD;
    public ConnectionFactory() {
    }
    /**
     * 在静态代码块中，获得属性文件中的driver,url,username,password
     */
    static{
        //step1:创建一个Properties对象
        Properties pro = new Properties();
        //step2:以流的形式读取属性文件中的内容
        InputStream is = Thread.currentThread().getContextClassLoader().getResourceAsStream("jdbc.properties");
        try {
            //step3:加载流is到p对象中
            pro.load(is);
            DB_DRIVER = pro.getProperty("driver");
            DB_URL = pro.getProperty("url");
            DB_USERNAME = pro.getProperty("username");
            DB_PASSWORD = pro.getProperty("password");
        }catch (IOException e){
            e.printStackTrace();
        }
    }
    /**
     * 该方法用来加载驱动，并获得数据库的连接对象
     *
     * @return 数据库连接对象conn
     */
    public static Connection getConnection(){
        Connection conn = null;
        try {
            //加载驱动
            Class.forName(DB_DRIVER);
        }catch (ClassNotFoundException e){
            e.printStackTrace();
        }
        try {
            conn = DriverManager.getConnection(DB_URL,DB_USERNAME,DB_PASSWORD);
        }catch (SQLException e){
            e.printStackTrace();
        }
        return conn;
    }
}

3）创建CloseFactory工厂类，用于关闭连接对象

package com.yyq.factory;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
/**
 * Created by gao on 16-4-13.
 */
public class CloseFactory {
    //关闭Connection
    public static void close(Connection conn){
        if (null != conn){
            try{
                conn.close();
            }catch (SQLException e){
                e.printStackTrace();
            }
        }
    }
    //关闭Statemnt
    public static void close(Statement stmt){
        if (null != stmt){
            try{
                stmt.close();
            }catch (SQLException e){
                e.printStackTrace();
            }
        }
    }
    //关闭ResultSet
    public static void close(ResultSet rs){
        if (null != rs){
            try {
                rs.close();
            }catch (SQLException e){
                e.printStackTrace();
            }
        }
    }
    //关闭用来执行Select的JDBC资源
    public static void close(ResultSet rs, Statement stmt, Connection conn){
        close(rs);
        close(stmt,conn);
    }
    public static void close(Statement stmt, Connection conn){
        close(stmt);
        close(conn);
    }
}

4）创建ContrlFactory工厂类，用于执行数据库操作

package com.yyq.factory;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
/**
 * Created by gao on 16-4-13.
 */
public class ContrlFactory {
    /**
    * 执行select语句
    */
    public static ResultSet executeQuery(String sql) throws Exception{
        ResultSet rs = null;
        Statement stmt = null;
        Connection conn = null;
        try {
            conn = ConnectionFactory.getConnection();
            stmt = conn.createStatement();
            rs = stmt.executeQuery(sql);
        }catch (SQLException e){
            throw e;
        }
        return rs;
    }
    /**
    * 执行Insert、Update、Delete语句
    */
    public static void executeUpdate(String sql) throws Exception{
        Connection conn = null;
        Statement stmt = null;
        try {
            conn = ConnectionFactory.getConnection();
            stmt = conn.createStatement();
            stmt.executeUpdate(sql);
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            CloseFactory.close(stmt,conn);
        }
    }
 }

5）测试类

package com.yyq;
import com.yyq.factory.CloseFactory;
import com.yyq.factory.ConnectionFactory;
import com.yyq.factory.ContrlFactory;
import org.junit.Test;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
/**
 * Created by gao on 16-4-13.
 */
public class JDBCTest {
    Connection conn = null;
    @Test
    public void connectionTest(){
        conn = ConnectionFactory.getConnection();
        if(null == conn){
            System.out.println("未获取数据库连接对象");
        }else {
            System.out.println("已获取数据库连接对象");
        }
    }
//    @Test
//    public void closeTest() throws SQLException {
//        connectionTest();
//        CloseFactory.close(null,null,conn);
//        if(null == conn){
//            System.out.println("数据库连接对象已关闭");
//        }else {
//            System.out.println("数据库连接对象未关闭");
//        }
//    }
    @Test
    public void contrlQueryTest() throws Exception {
        String sql = "select * from student;";
        ResultSet rs = ContrlFactory.executeQuery(sql);
        while (rs.next()){
            System.out.println("Id："+rs.getInt("id")+"\t姓名："+rs.getString("name")+"\t科目："
                    +rs.getString("class")+"\t分数："+rs.getInt("score"));
        }
    }
    @Test
    public void contrlInsertTest() throws Exception{
        String sql = "insert into student(name,score,class) values('sheng',88,'linxu')";
        ContrlFactory.executeUpdate(sql);
    }
}

6）项目结构图：