Java BasicDAO的详解

Posted 2022-05-09 路宇

一、BasicDAO的介绍

二、BasicDAO的示意图

三、完成BasicDAO的简单实例

1、创建BasicDAO类

//开发BasicDAO,是其他DAO的父类
public class BasicDAO<T> //泛型指定具体的类型
    private QueryRunner qr = new QueryRunner();

    //开发通用的DML方法，针对任意的表
    public int update(String sql, Object... parameters) 
        Connection connection = null;
        try 
            connection = JDBCUtilsByDruid.getConnection();
            int update = qr.update(connection, sql, parameters);
            return update;
         catch (SQLException e) 
            //将编译异常转换为运行异常，抛出
            throw new RuntimeException(e);
         finally 
            JDBCUtilsByDruid.close(null, null, connection);
        
    

    //返回多个对象(即查询的结果是多行)，针对任意表

    /**
     * @param sql        sql语句可以有?号
     * @param clazz      传入一个类的Class对象 比如Actor.class
     * @param parameters 传入? 的具体的值，可以是多个
     * @return 根据Actor.class 返回对应的ArrayList集合
     */
    public List<T> queryMulti(String sql, Class<T> clazz, Object... parameters) 
        Connection connection = null;
        try 
            connection = JDBCUtilsByDruid.getConnection();
            return qr.query(connection, sql, new BeanListHandler<T>(clazz), parameters);
         catch (SQLException e) 
            //将编译异常转换为运行异常，抛出
            throw new RuntimeException(e);
         finally 
            JDBCUtilsByDruid.close(null, null, connection);
        
    

    //查询单行结果的通用方法
    public T querySingle(String sql, Class<T> clazz, Object... parameters) 
        Connection connection = null;
        try 
            connection = JDBCUtilsByDruid.getConnection();
            return qr.query(connection, sql, new BeanHandler<T>(clazz), parameters);
         catch (SQLException e) 
            //将编译异常转换为运行异常，抛出
            throw new RuntimeException(e);
         finally 
            JDBCUtilsByDruid.close(null, null, connection);
        
    

    //查询单行单列的方法，即返回单值的方法
    public Object queryScalar(String sql, Object... parameters) 
        Connection connection = null;
        try 
            connection = JDBCUtilsByDruid.getConnection();
            return qr.query(connection, sql, new ScalarHandler(), parameters);
         catch (SQLException e) 
            //将编译异常转换为运行异常，抛出
            throw new RuntimeException(e);
         finally 
            JDBCUtilsByDruid.close(null, null, connection);
        
    

2、创建ActorDAO类继承BasicDAO类

public class ActorDAO extends BasicDAO<Actor>
    //1.就有BasicDao的方法
    //2.根据业务需求，可以编写特有的方法

3、创建domain,Actor类

//Actor对象 和 actor表的记录对应
public class Actor //JavaBean ,POJO,Domain对象
    private Integer id;
    private String name;
    private String sex;
    private Date borndate;
    private String phone;

    public Actor() //一定要给一个无参构造器[反射需要]
    

    public Actor(Integer id, String name, String sex, Date borndate, String phone) 
        this.id = id;
        this.name = name;
        this.sex = sex;
        this.borndate = borndate;
        this.phone = phone;
    

    public Integer getId() 
        return id;
    

    public void setId(Integer 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 Date getBorndate() 
        return borndate;
    

    public void setBorndate(Date borndate) 
        this.borndate = borndate;
    

    public String getPhone() 
        return phone;
    

    public void setPhone(String phone) 
        this.phone = phone;
    

    @Override
    public String toString() 
        return "Actor" +
                "id=" + id +
                ", name='" + name + '\\'' +
                ", sex='" + sex + '\\'' +
                ", borndate=" + borndate +
                ", phone='" + phone + '\\'' +
                '';
    

4、创建测试类TestDAO

public class TestDAO 
    //测试ActorDAO 对Actor表的crud操作
    @Test
    public void testActorDAO() 
        ActorDAO actorDAO = new ActorDAO();
        //1.查询多行记录
        List<Actor> actors = actorDAO.queryMulti("SELECT * FROM actor WHERE id >= ?", Actor.class, 2);
        System.out.println("===查询结果===");
        for (Actor actor : actors) 
            System.out.println(actor);
        


        //查询单行记录
        Actor actor = actorDAO.querySingle("SELECT * FROM actor WHERE id = ?", Actor.class, 2);
        System.out.println("===查询单行结果===");
        System.out.println(actor);

        //查询单行单例
        Object o = actorDAO.queryScalar("SELECT name FROM actor WHERE id = ?", 2);
        System.out.println("===查询单行单列===");
        System.out.println(o);

        //DML操作 (insert,delete,update)
//        int affectedRows = actorDAO.update("UPDATE actor SET NAME=? WHERE id = ?", "林青霞", 2);
//        int affectedRows = actorDAO.update("INSERT INTO actor VALUES(NULL,?,?,?,?)", "许三多", "男","1999-01-01","123456");
        int affectedRows = actorDAO.update("DELETE FROM actor WHERE id = ?", "5");
        System.out.println(affectedRows > 0 ? "执行成功" : "执行没有影响表");

    

输出结果如下

===查询结果===
Actorid=2, name='林青霞', sex='男', borndate=1980-01-03 08:00:00.0, phone='123456789'
Actorid=3, name='张三丰', sex='男', borndate=1999-01-10 08:00:00.0, phone='1234567890'
Actorid=5, name='许三多', sex='男', borndate=1999-01-01 08:00:00.0, phone='123456'
===查询单行结果===
Actorid=2, name='林青霞', sex='男', borndate=1980-01-03 08:00:00.0, phone='123456789'
===查询单行单列===
林青霞
执行成功

JDBCUtilsByDruid工具类的封装，看这篇文章传送门

Java 数据库连接池C3P0，德鲁伊(Druid)的详解 里面有对JDBCUtilsByDruid工具类的封装。