JDBC-setSavepoint,releaseSavepoint例子

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//STEP 1. Import required packages
import java.sql.*;
public class JDBCExample {
   // 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 = "username";
   static final String PASS = "password";
  
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: Set auto commit as false.
      conn.setAutoCommit(false);
      //STEP 5: Execute a query to delete statment with
      // required arguments for RS example.
      System.out.println("Creating statement...");
      stmt = conn.createStatement();
   //STEP 6: Now list all the available records.
      String sql = "SELECT id, first, last, age FROM Employees";
      ResultSet rs = stmt.executeQuery(sql);
      System.out.println("List result set for reference....");
      printRs(rs);
      // STEP 7: delete rows having ID grater than 104
      // But save point before doing so.
      Savepoint savepoint1 = conn.setSavepoint("ROWS_DELETED_1");
      System.out.println("Deleting row....");
      String SQL = "DELETE FROM Employees " +
                   "WHERE ID = 110";
      stmt.executeUpdate(SQL); 
      // oops... we deleted too wrong employees!
      //STEP 8: Rollback the changes afetr save point 2.
      conn.rollback(savepoint1);
    // STEP 9: delete rows having ID grater than 104
      // But save point before doing so.
      Savepoint savepoint2 = conn.setSavepoint("ROWS_DELETED_2");
      System.out.println("Deleting row....");
      SQL = "DELETE FROM Employees " +
                   "WHERE ID = 95";
      stmt.executeUpdate(SQL); 
   //STEP 10: Now list all the available records.
      sql = "SELECT id, first, last, age FROM Employees";
      rs = stmt.executeQuery(sql);
      System.out.println("List result set for reference....");
      printRs(rs);
      //STEP 10: Clean-up environment
      rs.close();
      stmt.close();
      conn.close();
   }catch(SQLException se){
      //Handle errors for JDBC
      se.printStackTrace();
      // If there is an error then rollback the changes.
      System.out.println("Rolling back data here....");
   try{
   if(conn!=null)
            conn.rollback();
      }catch(SQLException se2){
         se2.printStackTrace();
      }//end try
   }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
   public static void printRs(ResultSet rs) throws SQLException{
      //Ensure we start with first row
      rs.beforeFirst();
      while(rs.next()){
         //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);
     }
     System.out.println();
   }//end printRs()

                        

                            

                                
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