使用java读取数据库中的数据
时间: 2024-05-06 18:20:10 浏览: 13
以下是使用Java读取数据库中的数据的简单示例:
1. 导入所需的包和类
```
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
```
2. 建立数据库连接
```
String url = "jdbc:mysql://localhost:3306/testdb";
String username = "root";
String password = "password";
Connection conn = DriverManager.getConnection(url, username, password);
```
其中,url为数据库的地址,username和password为登录数据库的用户名和密码。
3. 执行SQL查询语句
```
Statement stmt = conn.createStatement();
String sql = "SELECT * FROM students";
ResultSet rs = stmt.executeQuery(sql);
```
其中,stmt为执行SQL语句的对象,sql为查询语句,rs为查询结果集。
4. 遍历结果集并输出数据
```
while (rs.next()) {
int id = rs.getInt("id");
String name = rs.getString("name");
int age = rs.getInt("age");
System.out.println("ID: " + id + ", Name: " + name + ", Age: " + age);
}
```
其中,rs.next()方法用于遍历查询结果集,rs.getInt()和rs.getString()方法用于获取指定列的数据。
5. 关闭连接和查询结果集
```
rs.close();
stmt.close();
conn.close();
```
完整代码示例:
```
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class ReadDataFromDatabase {
public static void main(String[] args) {
try {
// 建立数据库连接
String url = "jdbc:mysql://localhost:3306/testdb";
String username = "root";
String password = "password";
Connection conn = DriverManager.getConnection(url, username, password);
// 执行SQL查询语句
Statement stmt = conn.createStatement();
String sql = "SELECT * FROM students";
ResultSet rs = stmt.executeQuery(sql);
// 遍历结果集并输出数据
while (rs.next()) {
int id = rs.getInt("id");
String name = rs.getString("name");
int age = rs.getInt("age");
System.out.println("ID: " + id + ", Name: " + name + ", Age: " + age);
}
// 关闭连接和查询结果集
rs.close();
stmt.close();
conn.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
```