结果集未打开。验证自动提交是否关闭。 Apache Debry

问题描述

我正在使用apache derby作为我的数据库。我能够在数据库中执行插入操作。以下是试图显示我唯一的表'MAINTAB'的内容的代码的摘录。 java.sql.Connection的实例是'dbconn'。

I am using apache derby for my database. I am able to perform inserts into the database. The following is the excerpt from the code that attempts to display the contents of my only table 'MAINTAB'. The instance of java.sql.Connection is 'dbconn'.

    ResultSet word;

    Statement query;

    String getData="SELECT THEWORD FROM MAINTAB";
    try{
        System.out.println(dbconn.getAutoCommit());
        query = dbconn.createStatement();
        word = query.executeQuery(getData);
        query.close();

        dbconn.setAutoCommit(false);
        System.out.println(dbconn.getAutoCommit());

        for(;word.next();)
            System.out.println(word.getString(1));

    }catch(Throwable e){
        System.out.println("Table fetch failed or result data failed");}

以下是输出。

org.apache.derby.jdbc.EmbeddedDriver loaded.
Database testDB connected
true
false
Table fetch failed or result data failed

---SQLException Caught---

SQLState:   XCL16
Severity: 20000
Message:  ResultSet not open. Operation 'getString' not permitted. Verify that autocommit is OFF.
java.sql.SQLException: ResultSet not open. Operation 'getString' not permitted. Verify that autocommit is OFF.
    at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.Util.generateCsSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedConnection.newSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.ConnectionChild.newSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedResultSet.checkIfClosed(Unknown Source)
    at org.apache.derby.impl.jdbc.EmbedResultSet.getString(Unknown Source)
Closed connection
    at test.ShowData.main(ShowData.java:30)
Caused by: java.sql.SQLException: ResultSet not open. Operation 'getString' not permitted. Verify that autocommit is OFF.
    at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
    at org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(



Unknown Source)
    ... 9 more
Database shut down normally

---

当它首先要求验证AUTOCOMMIT是否为OFF时，我从Derby文档中发现默认情况下AUTOCOMMIT已打开为任何连接。所以，我使用dbconn.setAutoCommit（false）将其关闭。仍然会抛出错误。

---

When, it first asked to verify if AUTOCOMMIT is OFF, I have found from the Derby Documentation that AUTOCOMMIT is turned ON by default to any connection. So, I've turned it off using dbconn.setAutoCommit(false). Still, the error is thrown.

错误之前的输出说明结果集是在没有任何错误的情况下获取的。另请注意，即使我没有将AutoCommit设置为false，也会抛出相同的错误。介于两者之间，我正在日食上运行德比。

The output before the error explains that the result set was fetched without any error. Also, please note that the same error is thrown even if I do not set the AutoCommit to false. Between, I am running derby on eclipse.

推荐答案

问题是你已经关闭之前的 >阅读结果集。关闭查询，关闭结果集，从而导致ResultSet未打开错误的原因。您应该在最后 finally 块中关闭查询：

The problem is that you have closed your query before reading your resultset. Closing the query, closes the resultset, hence why you get the "ResultSet not open" error. You should close the query right at the end, in a finally block:

ResultSet word;

Statement query=null;

String getData="SELECT THEWORD FROM MAINTAB";
try{
    System.out.println(dbconn.getAutoCommit());
    query = dbconn.createStatement();
    word = query.executeQuery(getData);


    dbconn.setAutoCommit(false);
    System.out.println(dbconn.getAutoCommit());

    for(;word.next();)
        System.out.println(word.getString(1));

}catch(Throwable e){
    System.out.println("Table fetch failed or result data failed");
} finally{
    if(query!=null) {
        try {
             query.close();
        }
        catch(SQLException ex) {
              System.out.println("Could not close query");
        }
   }
}

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