Maven之jdbc连接数据库

这里需提前将maven环境配置好

链接: Maven环境配置

---

---

JDBC

Java Database Connectivity(java语言连接数据库)
JDBC本质----接口
接口都有调用者和实现者
面向接口调用，面向接口写实现类

---

创建Maven工程

1.新建Maven工程

2.仓库中获取mysql的驱动依赖

从https://mvnrepository.com/　仓库中获取mysql的驱动依赖

  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>8.0.29</version>
</dependency>

JDBC访问数据库步骤

1.Class.forName()加载驱动

 //加载驱动
 Class.forName("com.mysql.jdbc.Driver");

2.DriverManager获取Connection连接

    // 创建连接  有三个参数    第一个url   第二个 user  第三个 password
    // url    : 数据的地址    协议:什么样的数据库:数据库服务器的地址:端口号/数据库名称
    //  user  :  数据库的用户名
    //password : 数据库的密码
    //地址还可以添加参数  &useUnicode=true&characterEncoding=utf-8  为设置字符集为utf-8  专门针对乱码
    //useSSL=false   是否选择加密连接    

//获取connection连接
connection = DriverManager.getConnection(
    "jdbc:mysql://192.168.95.130:3306/jdbcstu",
    "root",
    "root"
);
System.out.println(connection);

3.创建Statement执行SQL语句

/*新增*/
String sql ="insert into master(name,age,gender,yearnum,did) value(?,?,?,?,?)";
String name ="张三";
Integer age =20;
String gender="男";
Integer yearnum=3;
Integer did =1;
//创建preparedStatement---防止SQL注入
preparedStatement =connection.prepareStatement(sql);
preparedStatement.setString(1,name);
preparedStatement.setInt(2,age);
preparedStatement.setString(3,gender);
preparedStatement.setInt(4,yearnum);
preparedStatement.setInt(5,did);
int num = preparedStatement.executeUpdate();
if (num>0){
   System.out.println("新增主人信息成功");
}

/*修改*/
String sql ="update master set age =? where pid=?";
Integer age = 18;
Integer pid =2;
preparedStatement =connection.prepareStatement(sql);
preparedStatement.setInt(1,age);
preparedStatement.setInt(2,pid);
int num =preparedStatement.executeUpdate();
if (num>0){
 System.out.println("修改主人信息成功");
}

/*删除*/
String sql="delete from master where pid =?";
preparedStatement =connection.prepareStatement(sql);
Integer pid=4;
preparedStatement.setInt(1,pid);
int num = preparedStatement.executeUpdate();
if (num>0){
System.out.println("删除主人信息成功");
}

4.返回ResultSet查询结果()

只有执行select语句才有查询结果集

 /*查询*/
String sql ="select pid ,m.name,age,gender,yearnum,d.name,health,love,strain,lytm from master m,dog d where m.did=d.id ";
preparedStatement =connection.prepareStatement(sql);
resultSet = preparedStatement.executeQuery();
System.out.println("\t\t信息表");
System.out.println("编号\t名字\t年龄\t性别\t经验值\t宠物名字\t\t健康值\t亲密度\t品种\t领养时间");
while (resultSet.next()){
System.out.print(resultSet.getInt("pid")+"\t");              System.out.print(resultSet.getString("m.name")+"\t");
System.out.print(resultSet.getInt("age")+"\t");               System.out.print(resultSet.getString("gender")+"\t");               System.out.print(resultSet.getInt("yearnum")+"\t\t");               System.out.print(resultSet.getString("d.name")+"\t\t");
System.out.print(resultSet.getInt("health")+"\t\t");
System.out.print(resultSet.getInt("love")+"\t\t");                System.out.print(resultSet.getString("strain")+"\t\t");
System.out.println(resultSet.getDate("lytm")+"\t");
}

5.释放资源

if (resultSet!=null){
  try {
    resultSet.close();
    } catch (SQLException e) {
    e.printStackTrace();
    }
      }
if (preparedStatement!=null){
  try {
    preparedStatement.close();
    } catch (SQLException e) {
    e.printStackTrace();
    }
      }
if (connection!=null){
  try {
    connection.close();
    } catch (SQLException e) {
    e.printStackTrace();
  }
   }