JDBC檢視結果集教學

以下是使用結果集一章中描述的幾個getInt和getString方法的範例。 該範例非常類似於瀏覽結果集部分中解釋的範例。

此範例程式碼是基於前面章節中完成的環境和資料庫設定編寫的。

複製並通過以下範例程式碼放在檔案：ViewingResultSet.java 中，然後編譯並執行如下 -

//STEP 1. Import required packages
import java.sql.*;

public class ViewingResultSet {
   // JDBC driver name and database URL
   static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
   static final String DB_URL = "jdbc:mysql://localhost/EMP";

   //  Database credentials
   static final String USER = "root";
   static final String PASS = "123456";

public static void main(String[] args) {
   Connection conn = null;
   Statement stmt = null;
   try{
      //STEP 2: Register JDBC driver
      Class.forName("com.mysql.jdbc.Driver");

      //STEP 3: Open a connection
      System.out.println("Connecting to database...");
      conn = DriverManager.getConnection(DB_URL,USER,PASS);

      //STEP 4: Execute a query to create statment with
      // required arguments for RS example.
      System.out.println("Creating statement...");
      stmt = conn.createStatement(
                           ResultSet.TYPE_SCROLL_INSENSITIVE,
                           ResultSet.CONCUR_READ_ONLY);
      String sql;
      sql = "SELECT id, first, last, age FROM Employees";
      ResultSet rs = stmt.executeQuery(sql);

      // Move cursor to the last row.
      System.out.println("Moving cursor to the last...");
      rs.last();

      //STEP 5: 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();

      //STEP 6: 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();

      //STEP 7: 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);

      //STEP 8: Clean-up environment
      rs.close();
      stmt.close();
      conn.close();
   }catch(SQLException se){
      //Handle errors for JDBC
      se.printStackTrace();
   }catch(Exception e){
      //Handle errors for Class.forName
      e.printStackTrace();
   }finally{
      //finally block used to close resources
      try{
         if(stmt!=null)
            stmt.close();
      }catch(SQLException se2){
      }// nothing we can do
      try{
         if(conn!=null)
            conn.close();
      }catch(SQLException se){
         se.printStackTrace();
      }//end finally try
   }//end try
   System.out.println("Goodbye!");
}//end main
}//end JDBCExample

編譯並執行如下 -

F:\worksp\jdbc>javac -Djava.ext.dirs=F:\worksp\jdbc\libs ViewingResultSet.java

F:\worksp\jdbc>java -Djava.ext.dirs=F:\worksp\jdbc\libs ViewingResultSet

執行上面程式碼，得到以下結果 -

F:\worksp\jdbc>java -Djava.ext.dirs=F:\worksp\jdbc\libs ViewingResultSet
Connecting to database...
Wed May 31 23:28:51 CST 2017 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
Creating statement...
Moving cursor to the last...
Displaying record...
ID: 103, Age: 30, First: Jack, Last: Ma
Moving cursor to the first row...
Displaying record...
ID: 100, Age: 28, First: Max, Last: Su
Moving cursor to the next row...
Displaying record...
ID: 101, Age: 25, First: Wei, Last: Wang
Goodbye!

F:\worksp\jdbc>