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。

The ResultSet interface contains dozens of methods for getting the data of the current row.

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 −

There is a get method for each of the possible data types, and each get method has two versions −

  1. One that takes in a column name.

  2. One that takes in a column index.

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 −

For example, if the column you are interested in viewing contains an int, you need to use one of the getInt() methods of ResultSet −

S.N.

Methods & Description

1

*public int getInt(String columnName) throws SQLException*Returns the int in the current row in the column named columnName.

2

*public int getInt(int columnIndex) throws SQLException*Returns the int in the current row in the specified column index. The column index starts at 1, meaning the first column of a row is 1, the second column of a row is 2, and so on.

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。

Similarly, there are get methods in the ResultSet interface for each of the eight Java primitive types, as well as common types such as java.lang.String, java.lang.Object, and java.net.URL.

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。

There are also methods for getting SQL data types java.sql.Date, java.sql.Time, java.sql.TimeStamp, java.sql.Clob, and java.sql.Blob. Check the documentation for more information about using these SQL data types.

以下是利用上述部分查看方式的示例。

Following is the example which makes use of few viewing methods described.

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。

This sample code has been written based on the environment and database setup done in the previous chapters.

将以下示例复制并粘贴到 TestApplication.java 中，如下进行编译和运行：

Copy and paste the following example in TestApplication.java, compile and run as follows −

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：

Now let us compile the above example as follows −

C:\>javac TestApplication.java
C:\>

运行 TestApplication 时，它会生成以下结果：

When you run TestApplication, it produces the following result −

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:\>