Java Mysql 简明教程
Java & MySQL - Viewing a ResultSet
ResultSet 接口包含几十个方法用于获取当前行中的数据。
对于所有可能的数据类型都有一个 get 方法,并且每个 get 方法有两个版本 −
-
一个接受列名称。
-
一个接受列索引。
例如,如果您感兴趣的列包含一个 int,您需要使用 ResultSet 的其中一个 getInt() 方法 −
S.N. |
Methods & Description |
1 |
*public int getInt(String columnName) throws SQLException*返回列名为 columnName 的当前行中的 int。 |
2 |
*public int getInt(int columnIndex) throws SQLException*返回指定列索引中当前行中的 int。列索引从 1 开始,这意味着行的第一列为 1,行的第二列为 2,依此类推。 |
同样,ResultSet 接口中有 get 方法用于八种 Java 原始类型以及 java.lang.String、java.lang.Object 和 java.net.URL 等常见类型。
还有方法用于获取 SQL 数据类型 java.sql.Date、java.sql.Time、java.sql.TimeStamp、java.sql.Clob 和 java.sql.Blob。查看文档了解更多有关使用这些 SQL 数据类型的信息。
以下是利用上述部分查看方式的示例。
此示例代码基于先前章节中完成的环境和数据库设置编写。
将以下示例复制并粘贴到 TestApplication.java 中,如下进行编译和运行:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class TestApplication {
static final String DB_URL = "jdbc:mysql://localhost/TUTORIALSPOINT";
static final String USER = "guest";
static final String PASS = "guest123";
static final String QUERY = "SELECT id, first, last, age FROM Employees";
public static void main(String[] args) {
// Open a connection
try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
Statement stmt = conn.createStatement(
ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_READ_ONLY);
ResultSet rs = stmt.executeQuery(QUERY);
) {
// Move cursor to the last row.
System.out.println("Moving cursor to the last...");
rs.last();
// Extract data from result set
System.out.println("Displaying record...");
//Retrieve by column name
int id = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");
// Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
// Move cursor to the first row.
System.out.println("Moving cursor to the first row...");
rs.first();
// Extract data from result set
System.out.println("Displaying record...");
// Retrieve by column name
id = rs.getInt("id");
age = rs.getInt("age");
first = rs.getString("first");
last = rs.getString("last");
// Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
// Move cursor to the first row.
System.out.println("Moving cursor to the next row...");
rs.next();
// Extract data from result set
System.out.println("Displaying record...");
id = rs.getInt("id");
age = rs.getInt("age");
first = rs.getString("first");
last = rs.getString("last");
// Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
现在让我们如下编译上述示例:
C:\>javac TestApplication.java
C:\>
运行 TestApplication 时,它会生成以下结果:
C:\>java TestApplication
Moving cursor to the last...
Displaying record...
ID: 103, Age: 30, First: Sumit, Last: Mittal
Moving cursor to the first row...
Displaying record...
ID: 100, Age: 18, First: Zara, Last: Ali
Moving cursor to the next row...
Displaying record...
ID: 101, Age: 25, First: Mehnaz, Last: Fatma
C:\>