JDBC入门案例
步骤
- 加载数据库驱动
- 建立数据库链接
- 创建preparedStatement
- 处理数据
- 关闭数据
入门案例
准备数据库
#新建表
CREATE TABLE student (
sid INT(10) PRIMARY KEY,
sname VARCHAR(50),
age INT(10),
gender VARCHAR(10)
);
#插入五条数据
INSERT INTO student (sid,sname,age,gender) VALUES (1,'asd',17,'male');
INSERT INTO student (sid,sname,age,gender) VALUES (2,'fgh',18,'female');
INSERT INTO student (sid,sname,age,gender) VALUES (3,'jkl',21,'male');
INSERT INTO student (sid,sname,age,gender) VALUES (4,'qwe',20,'female');
INSERT INTO student (sid,sname,age,gender) VALUES (5,'yui',19,'male');
编写Java程序
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
// 导入的包都为java.sql的包，
public class test_jdbc {
public static void main(String[] args) {
test_jdbc test = new test_jdbc();
//在这里调用对象的方法来运行就可以了
test.deleteStudent();
}
//查询所有的学生
public void selectStudent() {
Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
try {
//1.加载数据库驱动
Class.forName("com.mysql.jdbc.Driver");
//2.建立数据库的连接
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbctest","root","x5");
//3.创建statement
statement = connection.createStatement();
//statement
String sql = "select * from student";
resultSet = statement.executeQuery(sql);
//处理数据
while (resultSet.next()) {
int sid = resultSet.getInt("sid");
String sname = resultSet.getString("sname");
int age = resultSet.getInt("age");
String gender = resultSet.getString("gender");
//将查询的数据写入对象
Student student = new Student();
student.setSid(sid);
student.setSname(sname);
student.setAge(age);
student.setGender(gender);
System.out.println(student);
}
} catch (Exception e) {
System.out.println(e.toString());
} finally {
//不为空就关闭
if(resultSet != null) {
try {
resultSet.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
resultSet = null;
}
//不为空就关闭
if(statement != null) {
try {
statement.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
statement = null;
}
//不为空就关闭
if(connection != null) {
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
connection = null;
}
System.out.println("==========查询成功==========");
}
}
public void addStudent() {
Connection connection = null;
PreparedStatement preparedStatement = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbctest","root","x5");
// ?是占位符，会在后面写入
String sql = "insert into student values (?,?,?,?)";
preparedStatement = connection.prepareStatement(sql);
//下面的1，2，3，4分别代表着上面sql语句中的第几个占位符
preparedStatement.setInt(1, 1010);
preparedStatement.setString(2, "hjh");
preparedStatement.setInt(3, 22);
preparedStatement.setString(4, "male");
//执行sql语句
preparedStatement.executeUpdate();
} catch (Exception e) {
System.out.println(e.toString());
} finally {
//不为空就关闭
if(connection != null) {
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
connection = null;
}
//不为空就关闭
if(preparedStatement != null) {
try {
preparedStatement.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
preparedStatement = null;
}
System.out.println("==========添加成功==========");
}
}
public void deleteStudent() {
Connection connection = null;
PreparedStatement preparedStatement = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://localhost/jdbctest", "root", "x5");
//从学生表中删除学号为？的学生
String sql = "delete from student where sid = ?";
preparedStatement = connection.prepareStatement(sql);
//写入1010，删除学号为1010的学生
preparedStatement.setInt(1, 1010);
//执行sql语句
preparedStatement.executeUpdate();
} catch (Exception e) {
// TODO: handle exception
}finally {
//不为空就关闭
if(connection != null) {
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
connection = null;
}
//不为空就关闭
if(preparedStatement != null) {
try {
preparedStatement.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
preparedStatement = null;
}
System.out.println("==========删除成功==========");
}
}
public void updateStudent() {
Connection connection = null;
PreparedStatement preparedStatement = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbctest","root","x5");
//把学生表中sid为？的学生性别更改为？
String sql = "update student set gender = ? where sid = ?";
preparedStatement = connection.prepareStatement(sql);
//把学生表中sid为1010 的学生性别更改为female(女)
preparedStatement.setString(1, "female");
preparedStatement.setInt(2, 1010);
//执行sql语句
preparedStatement.executeUpdate();
} catch (Exception e) {
// TODO: handle exception
}finally {
//不为空就关闭
if(connection != null) {
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
connection = null;
}
//不为空就关闭
if(preparedStatement != null) {
try {
preparedStatement.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
preparedStatement = null;
}
System.out.println("==========修改成功==========");
}
}
public void findStudent() {
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbctest","root","x5");
//查询学生表中学生姓名为？的学生
String sql = "select * from student where sname = ?";
preparedStatement = connection.prepareStatement(sql);
//查询学生表中学生姓名为hjh 的学生
preparedStatement.setString(1, "hjh");
//将sql语句查询的结果放入resultSet中
resultSet = preparedStatement.executeQuery();
while( resultSet.next()) {
int sid = resultSet.getInt("sid");
String sname = resultSet.getString("sname");
int age = resultSet.getInt("age");
String gender = resultSet.getString("gender");
//打印
System.out.println("Student [sid=" + sid + ", sname=" + sname + ", age=" + age + ", gender=" + gender + "]");
}
} catch (Exception e) {
// TODO: handle exception
}finally {
//不为空就关闭
if(connection != null) {
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
connection = null;
}
//不为空就关闭
if(preparedStatement != null) {
try {
preparedStatement.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
preparedStatement = null;
}
System.out.println("==========查询成功==========");
}
}
}
