如何從單個 CallableStatement 獲得多個結果集？

Question

當我從命令行調用存儲過程時，我得到以下信息。

CALL `events`.`get_event_by_id`(10)

+---------+----------+-------------+---------------------+---------------------+---------------------+--------+----------+
| evet_id | name     | description | starttime           | endtime             | last_modified       | active | addre_id |
+---------+----------+-------------+---------------------+---------------------+---------------------+--------+----------+
|      10 | samole 3 | sanely      | 2013-11-27 17:37:00 | 2013-11-27 18:09:00 | 2013-11-27 09:37:42 |      1 |       20 |
+---------+----------+-------------+---------------------+---------------------+---------------------+--------+----------+
1 row in set (0.00 sec)

+---------+------------+---------+
| user_id | username   | picture |
+---------+------------+---------+
|       1 | jamess2000 | NULL    |
|       2 | yferna2012 | NULL    |
+---------+------------+---------+
2 rows in set (0.00 sec)

+----------+------------------------------+---------------------+-------------+--------+
| addre_id | street                       | name                | description | active |
+----------+------------------------------+---------------------+-------------+--------+
|       20 | Schieffelin                  | Manhattan Ville Loc | NULL        |      1 |
+----------+------------------------------+---------------------+-------------+--------+

這是我的 Java 代碼片段

String SP_GET_EVENT_BY_ID = "CALL `events`.`get_event_by_id`(?)";
String PROC_PARAM_EVENT_ID = "evet_id";
mCallableStatement = mConnection.prepareCall(SP_GET_EVENT_BY_ID);
mCallableStatement.setInt(10, PROC_PARAM_EVENT_ID);

當我執行語句時，只返回 event_table 結果。 我閱讀了以下查詢：

ResultSet reader = mCallableStatement.executeQuery();

while(reader.next())
{
   //etc..... here i assign db values to properties. 
}

我試圖避免向數據庫發出多個請求，因為它非常慢（300 毫秒，取決於結果的數量）

甚至有可能嗎？

Answer 1

我發現了這篇很棒的文章。 http://www.herongyang.com/JDBC/MySQL-CallableStatement-Multiple-ResulSet.html

這是那篇文章中的代碼。

/**
 * MySqlCallMultipleResultSet.java
 * Copyright (c) 2007 by Dr. Herong Yang. All rights reserved.
 */
import java.sql.*;
public class MySqlCallMultipleResultSet {
  public static void main(String [] args) {
    Connection con = null;
    try {
      com.mysql.jdbc.jdbc2.optional.MysqlDataSource ds 
        = new com.mysql.jdbc.jdbc2.optional.MysqlDataSource();
      ds.setServerName("localhost");
      ds.setPortNumber(3306);
      ds.setDatabaseName("HerongDB");
      ds.setUser("Herong");
      ds.setPassword("TopSecret");
      con = ds.getConnection();

// Create CallableStatement
      CallableStatement cs = con.prepareCall("CALL HeadTail(?)");

// Register OUT parameters
      cs.registerOutParameter(1, java.sql.Types.INTEGER);     

// Execute the CALL statement and expecting multiple result sets
      boolean isResultSet = cs.execute();

// First ReulstSet object
      if (!isResultSet) {
        System.out.println("The first result is not a ResultSet.");
        return;
      }

// First ReulstSet object
      System.out.println("Head of the table:");
      ResultSet res = cs.getResultSet();
      while (res.next()) {
        System.out.println("  "+res.getInt("ID")
          +", "+res.getString("FirstName")
          +", "+res.getString("LastName")
          +", "+res.getTimestamp("ModTime"));

      }
      res.close();

// Move to the next result
      isResultSet = cs.getMoreResults();
      if (!isResultSet) {
        System.out.println("The next result is not a ResultSet.");
        return;
      }

// Second ReulstSet object
      System.out.println("Tail of the table:");
      res = cs.getResultSet();
      while (res.next()) {
        System.out.println("  "+res.getInt("ID")
          +", "+res.getString("FirstName")
          +", "+res.getString("LastName")
          +", "+res.getTimestamp("ModTime"));

      }
      res.close();

// Retrieve OUT parameters
      System.out.println("Total number of records: "+cs.getInt(1));

// Close resource
      cs.close();

      con.close();
    } catch (Exception e) {
      System.err.println("Exception: "+e.getMessage());
      e.printStackTrace();
    }
  }
}

Answer 2

public static void executeProcedure(Connection con) {
   try {
      CallableStatement stmt = con.prepareCall(...);
      .....  //Set call parameters, if you have IN,OUT, or IN/OUT parameters

      boolean results = stmt.execute();
      int rsCount = 0;

      // Loop through the available result sets.
      while (results) {
           ResultSet rs = stmt.getResultSet();

           // Retrieve data from the result set.
           while (rs.next()) {
               // using rs.getxxx() method to retrieve data
           }

           rs.close();

           // Check for next result set
           results = stmt.getMoreResults();
      } 

      stmt.close();
   }
   catch (Exception e) {
      e.printStackTrace();
   }
}

Answer 3

根據Statement.getMoreResults()的 Javadocs，您還應該在查找更多結果集時檢查getUpdateCount() != -1 。

此代碼適用於 Sybase 以及可能適用於許多其他數據庫：

    try (Connection conn = DriverManager.getConnection(url, username, password);) {
        Class.forName("com.sybase.jdbc4.jdbc.SybDriver");
        CallableStatement call = conn.prepareCall("{call events.get_event_by_id(?)}");
        call.setInt("@evet_id", 10);
        boolean moreResults = call.execute();
        int updateCount = call.getUpdateCount();    
        while (moreResults || updateCount != -1) {
            if (moreResults) {
                ResultSet rs = call.getResultSet();
                processResults(rs);    
            }
            moreResults = call.getMoreResults();
            updateCount = call.getUpdateCount();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }

https://docs.oracle.com/javase/7/docs/api/java/sql/Statement.html#getMoreResults()