Mybatis从入门到精通——JDBC使用回顾（2）

清疚 2023-07-12 09:23 37阅读 0赞

# 一、简要说明 #

不管是Mybatis还是Hibernate都是对JDBC的二次封装，在使用JDBC之前，我们先回顾一下JDBC的使用。

# #

# 二、准备工作 #

## 1.maven依赖 ##

<dependencies>
                 
                <dependency>
                    <groupId>mysql</groupId>
                    <artifactId>mysql-connector-java</artifactId>
                    <version>8.0.18</version>
                </dependency>
    
                
                <dependency>
                    <groupId>junit</groupId>
                    <artifactId>junit</artifactId>
                    <version>4.12</version>
                </dependency>
    
            </dependencies>

## 2.实体类 ##

public class Person {
    
        private Integer id;
    
        private String name;
    
        private String sex;
    
        private String telephone;
    
        private String address;
    
        private Integer age;
    
        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 String getTelephone() {
            return telephone;
        }
    
        public void setTelephone(String telephone) {
            this.telephone = telephone;
        }
    
        public String getAddress() {
            return address;
        }
    
        public void setAddress(String address) {
            this.address = address;
        }
    
        public Integer getAge() {
            return age;
        }
    
        public void setAge(Integer age) {
            this.age = age;
        }
    
        @Override
        public String toString() {
            return "Person{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", sex='" + sex + '\'' +
                    ", telephone='" + telephone + '\'' +
                    ", address='" + address + '\'' +
                    ", age=" + age +
                    '}';
        }
    }

# 3.sql资源 #

DROP TABLE IF EXISTS `person`;
    CREATE TABLE `person` (
      `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
      `name` varchar(30) NOT NULL COMMENT '名字',
      `sex` char(1) NOT NULL DEFAULT '男' COMMENT '性别',
      `telephone` varchar(11) DEFAULT NULL COMMENT '手机号',
      `address` varchar(50) DEFAULT NULL COMMENT '地址',
      `age` tinyint(4) DEFAULT NULL COMMENT '年龄',
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=1295453 DEFAULT CHARSET=utf8;
    
    
    INSERT INTO `person` VALUES ('1', 'xy', '男', '123456', '测试', '18');
    INSERT INTO `person` VALUES ('2', 'ceshi', '女', '123456789', '美国', '20');
    INSERT INTO `person` VALUES ('3', 'ceshi', '女', '123456789', '美国', '21');

# 三、JDBC使用说明 #

JDBC具体使用步骤共分为六步：

1.注册驱动

2.通过驱动管理器（DriverManager）获取连接（Connection）

3.通过连接（Connection）获取数据库操纵对象（Statement）

4.通过数据库操纵对象（Statement）执行SQL

5.获取执行后的结果集（ResultSet），并进行结果处理

6.释放以上对象的资源（先使用的后释放）

具体步骤代码及测试代码如下：

public class MybatisTest {
    
        @Test
        public void test() throws ClassNotFoundException {
            String username = "root";
            String password = "123456";
            Connection connection = null;
            Statement statement = null;
            ResultSet resultSet = null;
            String url = "jdbc:mysql://localhost:3306/mybatis_study?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT%2B8";
            //1.注册驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            try {
                //2.获取数据库连接
                connection = DriverManager.getConnection(url, username, password);
                //3.获取一个Statement对象
                statement = connection.createStatement();
                String sql = "select * from person limit 1";
                //4.执行sql
                resultSet = statement.executeQuery(sql);
                //5返回结果处理
                Person person = new Person();
                while (resultSet.next()) {
                    person.setId(resultSet.getInt("id"));
                    person.setAge(resultSet.getInt("age"));
                    person.setName(resultSet.getString("name"));
                    person.setAddress(resultSet.getString("address"));
                    person.setSex(resultSet.getString("sex"));
                    person.setTelephone(resultSet.getString("telephone"));
                }
                System.out.println(person);
            }catch (SQLException e) {
                e.printStackTrace();
            }finally {
                //6.释放连接
                if(resultSet != null) {
                    try {
                        resultSet.close();
                    } catch (SQLException e) {
                        e.printStackTrace();
                    }finally {
                        try {
                            if(statement != null) {
                                statement.close();
                            }
                        } catch (SQLException e) {
                            e.printStackTrace();
                        }finally {
                            if(connection != null) {
                                try {
                                    connection.close();
                                } catch (SQLException e) {
                                    e.printStackTrace();
                                }
                            }
                        }
                    }
                }
            }
        }
    }