"Operation not allowed after ResultSet closed"数据源和爬虫4j

Question

在阅读了很多类似的问题后，我还没有找到一个适合我的解决方案。

我有这些方法:

在crawler4j控制器中，我这样做:

        ArrayList<String> urls = Urls.getURLs(100);
    for (String s : urls) {
        System.out.println("Adding URL: " + s);
        controller.addSeed(s);
    }

这是getURLs():

    public static ArrayList<String> getURLs(int number) {
    ArrayList<String> list = new ArrayList<String>();

    String getStatement = "select * from " + Configurations.getStringProperty("mysql.urls.db_name", "urls") + " where retrieved=0 limit "
            + Configurations.getStringProperty("mysql.urls.limit", "100") + ";";
    ResultSet rs;
    rs = Databaseclient.executeStatement(getStatement);


    try {
        while (rs.next()) {
            list.add(rs.getString("url"));
            // Databaseclient.executeStatement("update urls set retrieved = true where id = "
            // + rs.getInt("id") + ";");
        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        try {
            rs.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    return list;
}

这是我的executeStatement():

public static ResultSet executeStatement(String s) {
    Connection connection = null;
    Statement statement = null;
    ResultSet resultSet = null;
    try {
        // fetch a connection
        connection = DataSource.getInstance().getConnection();
        if (connection != null) {
            statement = connection.createStatement();
            resultSet = statement.executeQuery(s);
        }
    } catch (SQLException e) {
        System.out.println("A SQLException occured executing the Statement");
        e.printStackTrace();
    } catch (IOException e) {
        System.out.println("A IOException occured executing the Statement");
        e.printStackTrace();
    } catch (PropertyVetoException e) {
        System.out.println("A PropertyVetoException occured executing the Statement");
        e.printStackTrace();
    } finally {
        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                System.out.println("A SQLException occured executing the Statement");
                e.printStackTrace();
            }
        }
        if (statement != null) {
            try {
                statement.close();
            } catch (SQLException e) {
                System.out.println("A SQLException occured executing the Statement");
                e.printStackTrace();
            }
        }
        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                System.out.println("A SQLException occured executing the Statement");
                e.printStackTrace();
            }
        }
    }
    return resultSet;
}

我得到错误

java.sql.SQLException: Operation not allowed after ResultSet closed
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1094)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:997)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:983)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:928)
at com.mysql.jdbc.ResultSetImpl.checkClosed(ResultSetImpl.java:799)
at com.mysql.jdbc.ResultSetImpl.next(ResultSetImpl.java:6982)
at database.Urls.getURLs(Urls.java:27)
at crawler.Controller.main(Controller.java:53)

哪一行是

            while (rs.next()) {

在我的getURLs()方法。

我做错了什么?在获取语句和while循环之间没有可以关闭语句的代码。

Answer 1

你的代码有点偏离，但是如果我理解你的话，那么不要在你的executeStatement方法的最后块关闭你的ResultSet

public static ResultSet executeStatement(Connection connection, 
    Statement statement, String s) {
  ResultSet resultSet = null;
  try {
    if (statement != null) {
      resultSet = statement.executeQuery(s);
    }
  } catch (SQLException e) {
    System.out.println("A SQLException occured executing the Statement");
    e.printStackTrace();
  } catch (IOException e) {
    System.out.println("A IOException occured executing the Statement");
    e.printStackTrace();
  } catch (PropertyVetoException e) {
    System.out.println("A PropertyVetoException occured executing the Statement");
    e.printStackTrace();
  }
  return resultSet;
}

然后你需要传递一个连接和语句，你会得到一个ResultSet返回。此外，调用者应该在完成ResultSet后关闭所有三个。