c3p0实现对数据库的增删改查（JDBC加强版）

1.先将jar包导好（其中第二个和第三个不用导）：

2.创建一个c3p0带.xml的文件且放在src目录下：

3.先创建一个学生类：

public class Student {
    private  int id;
    private String name;
    private String sex;
    private String brithday;

    public Student() {
    }

    public Student(int id, String name, String sex, String brithday) {
        this.id = id;
        this.name = name;
        this.sex = sex;
        this.brithday = brithday;
    }

    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 getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getBrithday() {
        return brithday;
    }

    public void setBrithday(String brithday) {
        this.brithday = brithday;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", brithday='" + brithday + '\'' +
                '}';
    }
}

4.创建C3P0Util

public class C3P0Util {
    //得到一个数据源
    private static ComboPooledDataSource dataSource = new ComboPooledDataSource();

    public static ComboPooledDataSource getDataSource() {
        return dataSource;
    }
    //从数据源中得到一个连接对象
    public static Connection getConnection() {
        try {
            return dataSource.getConnection();
        } catch (SQLException e) {
            throw new ExceptionInInitializerError("服务器错误");
        }
    }

    //关闭资源
    public static void release(ResultSet rs, Statement stmt, Connection conn) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

5.创建一个ManagerThreadLocal类来保证线程安全

public class ManagerThreadLocal {
    private static ThreadLocal tl = new ThreadLocal<>();

    //得到一个连接
    public static Connection getConnection(){
        Connection conn = tl.get(); //从当前线程中取出一个连接
        if (conn == null){
            conn = C3P0Util.getConnection();    //从池中取一个
            tl.set(conn);   //把conn对象放入到当前对象线程中
        }
        return conn;
    }

    //开始事务
    public static void startTransacation(){
        try {
            Connection conn = getConnection();
            conn.setAutoCommit(false);   //从当前线程对象取出连接，并开始事务
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static void commit(){
        try {
            getConnection().commit();   //提交事务
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static void rollback(){
        try {
            getConnection().rollback(); //回滚事务
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static void close(){
        try {
            getConnection().close();    //把连接放回池中
            tl.remove();    //把当前线程对象中的conn移除
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

6.创建一个实现增删改查功能的类StudentDAO

public class StudentDAO {
    /**
     * 增加数据库里面一条学生对象信息的方法
     *
     * @param s
     * @return
     */
    public static void insert(Student s){
        QueryRunner qr = new QueryRunner();
        try {
            qr.update(ManagerThreadLocal.getConnection(),"INSERT INTO `student`(`id`,`name`, `sex`, `brithday`) VALUES (?,?,?,?)",
                    s.getId(),s.getName(),s.getSex(),s.getBrithday());
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            ManagerThreadLocal.close();
        }
    }

    /**
     * 根据数据库id改名字性别和生日的方法
     *
     * @param s
     * @return
     * @throws
     */
    public static void update(Student s) {
        QueryRunner qr = new QueryRunner();
        try {
            qr.update(ManagerThreadLocal.getConnection(),"UPDATE `student` SET `name` = ?, `sex` = ?, `brithday` = ? WHERE `id` = ?",
                    s.getName(),s.getSex(),s.getBrithday(),s.getId());
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            ManagerThreadLocal.close();
        }
    }

    /**
     * 根据对象名删除数据库对象信息的方法
     *
     * @param
     * @return
     * @throws SQLException
     */
    public static void delete(String name) {
        QueryRunner qr = new QueryRunner();
        try {
            qr.update(ManagerThreadLocal.getConnection(),"DELETE FROM `student` WHERE `name` = ?",name);
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            ManagerThreadLocal.close();
        }
    }

    /**
     * 查询表格的方法
     *
     * @throws SQLException
     */
    public static List select(){
        QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
        List students = null;
        try {
            students = qr.query("SELECT * FROM `student`;", new BeanListHandler<>(Student.class));
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            ManagerThreadLocal.close();
        }
        return students;
    }
}

7.测试类（可以实现选择菜单的一个测试类，可以自己根据提示来）

public class Test {
    private static int op = 0;
    public static void main(String[] args) throws SQLException {
        while (showMenu()){
            switch (op) {
                case 0:
                    add();
                    break;
                case 1:
                    remove();
                    break;
                case 2:
                    change();
                    break;
                case 3:
                    search();
                    break;
                case 4:
                    return;
            }
        }
    }

    public static boolean showMenu(){
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入您要对表格的操作按键（0-4）");
        System.out.println("0:增添对象");
        System.out.println("1:删除对象");
        System.out.println("2:改变对象属性");
        System.out.println("3:查询表格");
        System.out.println("4:退出选项");
        op = sc.nextInt();
        if (op>=0 && op<=4){
            return true;
        }else {
            System.out.println("请根据条件重新输入符合条件的数值");
            return false;
        }
    }

    public static void search() {
        List Students = StudentDAO.select();
        for (Student s : Students)
            System.out.printf("%d\t%s\t%s\t%s\n",s.getId(), s.getName(), s.getSex(), s.getBrithday());
    }

    public static void add(){
        System.out.println("请分别输入ID,姓名，性别，生日");
        Scanner sc=new Scanner(System.in);
        int id = sc.nextInt();
        String name = sc.next();
        String sex = sc.next();
        String bri = sc.next();
        Student s = new Student(id,name,sex,bri);
        StudentDAO.insert(s);
    }

    public static void remove(){
        System.out.println("请输入您要删除对象的姓名");
        Scanner sc=new Scanner(System.in);
        String name = sc.next();
        StudentDAO.delete(name);
    }

    public static void change(){
        System.out.println("请分别输入ID,姓名，性别，生日");
        Scanner sc=new Scanner(System.in);
        int id = sc.nextInt();
        String name = sc.next();
        String sex = sc.next();
        String bri = sc.next();
        Student s = new Student(id,name,sex,bri);
        StudentDAO.update(s);
    }
}

 

我们可以看到当我们不选择跳出时，我们不用再次运行 ，而是可以继续选择菜单。