JDBC 中的 CONCUR_UPDATABLE ResultSet 是什么?解释一下?
jdbcjava 8programmingobject oriented programming更新于 2025/1/22 5:00:17
它是 ResultSet 类的一个常量，表示可更新 ResultSet 对象的并发模式。通常，您会将其作为值传递给 createStatement() 方法。
Statement createStatement(int resultSetType, int resultSetConcurrency);
以此并发模式为 ResultSet 的 ResultSet 是可更新的。也就是说，一旦您获取到 ResultSet 对象，就可以更新其内容。
示例
假设数据库中有一个名为 Employee 的表，其内容如下:
+----+---------+--------+----------------+ | Id | Name | Salary | Location | +----+---------+--------+----------------+ | 1 | Amit | 3000 | Hyderabad | | 2 | Kalyan | 4000 | Vishakhapatnam | | 3 | Renuka | 6000 | Delhi | | 4 | Archana | 96000 | Mumbai | | 5 | Sumith | 11000 | Hyderabad | | 6 | Rama | 11000 | Goa | | 7 | Mahesh | 5300 | Vishakhapatnam | | 8 | Ramesh | 12000 | Hyderabad | | 9 | Suresh | 7600 | Pune | | 10 | Santosh | 96000 | Mumbai | +----+---------+--------+----------------+
以下示例将员工的工资值增加 5000 并打印结果。由于我们在其中创建的 ResultSet 是可更新的，因此您可以更新它并显示值。
import java.sql.*;
public class Updatable {
public static void main(String [] args) throws Exception {
//注册驱动程序
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//获取连接
String mysqlUrl = "jdbc:mysql://localhost/TestDB";
Connection con = DriverManager.getConnection(mysqlUrl, "root", "password");
System.out.println("连接已建立......");
//创建 Statement 对象
Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_UPDATABLE);
//检索数据
ResultSet rs = stmt.executeQuery("select * from Employees");
//打印表格内容
System.out.println("Contents of the table: ");
rs.beforeFirst();
while(rs.next()) {
System.out.print("ID: " + rs.getInt("id"));
System.out.print(", Salary: " + rs.getInt("Salary"));
System.out.print(", Name: " + rs.getString("Name"));
System.out.println(", Location: " + rs.getString("Location"));
}
System.out.println();
//将指针移动到 ResultSet 中的起始位置
rs.beforeFirst();
//将每位员工的工资更新 5000
while(rs.next()) {
//按列名检索
int newSal = rs.getInt("Salary") + 5000;
rs.updateInt( "Salary", newSal );
rs.updateRow();
}
System.out.println("Contents of the ResultSet after increasing salaries");
rs.beforeFirst();
while(rs.next()) {
System.out.print("ID: " + rs.getInt("id"));
System.out.print(", Salary: " + rs.getInt("Salary"));
System.out.print(", Name: " + rs.getString("Name"));
System.out.println(", Location: " + rs.getString("Location"));
}
System.out.println();
}
}
输出
连接已建立...... Contents of the table: ID: 1, Salary: 3000, Name: Amit, Location: Hyderabad ID: 2, Salary: 4000, Name: Kalyan, Location: Vishakhapatnam ID: 3, Salary: 6000, Name: Renuka, Location: Delhi ID: 4, Salary: 96000, Name: Archana, Location: Mumbai ID: 5, Salary: 11000, Name: Sumith, Location: Hyderabad ID: 6, Salary: 11000, Name: Rama, Location: Goa ID: 7, Salary: 5300, Name: Mahesh, Location: Vishakhapatnam ID: 8, Salary: 12000, Name: Ramesh, Location: Hyderabad ID: 9, Salary: 7600, Name: Suresh, Location: Pune ID: 10, Salary: 96000, Name: Santosh, Location: Mumbai Contents of the ResultSet after increasing salaries ID: 1, Salary: 8000, Name: Amit, Location: Hyderabad ID: 2, Salary: 9000, Name: Kalyan, Location: Vishakhapatnam ID: 3, Salary: 11000, Name: Renuka, Location: Delhi ID: 4, Salary: 101000, Name: Archana, Location: Mumbai ID: 5, Salary: 16000, Name: Sumith, Location: Hyderabad ID: 6, Salary: 16000, Name: Rama, Location: Goa ID: 7, Salary: 10300, Name: Mahesh, Location: Vishakhapatnam ID: 8, Salary: 17000, Name: Ramesh, Location: Hyderabad ID: 9, Salary: 12600, Name: Suresh, Location: Pune ID: 10, Salary: 101000, Name: Santosh, Location: Mumbai
