java – 使用jdbc澄清oracle中的游标

我遇到的情况是我使用的第三方开源产品在Oracle中没有游标并且收到错误:java.sql.SQLException:ORA-01000:超出最大打开游标数

我的最大游标设置为1000,我试图弄清楚达到此限制的代码是否正在执行错误操作,或者我是否只需要增加限制.

经过一些调查后,我在代码中找到了一个创建ResultSet的点,从而使我的打开游标数增加1.但是,该ResultSet在使用后很快就会关闭….但是光标数仍保持原样.我能够在第三方开源项目之外的简单JDBC应用程序中重现逻辑.

package gov.nyc.doitt.cursor;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class CursorTest {
    public static void main(String[] args) {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;

        try {
            Class.forName("oracle.jdbc.driver.OracleDriver");
            conn = DriverManager.getConnection("jdbc:oracle:thin:@myhost:1537:mydb", "username", "password");

            // as expected: there are 0 cursors associated with my session at this point

            ps = conn.prepareStatement("select my_column from my_table where my_id = ?");
            ps.setInt(1, 86);

            // as expected: there are 0 cursors associated with my session at this point

            rs = ps.executeQuery(); // opens 1 cursor

            // as expected: there is 1 open cursor associated with my session at this point
        } catch (Throwable t) {
            t.printStackTrace();
        } finally {
            // as expected: there is 1 open cursor associated with my session at this point
            try {
                rs.close();
            } catch (SQLException e) {
                System.err.println("Unable to close rs");
            }
            // not expected: there is still 1 open cursor associated with my session at this point
            try {
                ps.close();
            } catch (SQLException e) {
                System.err.println("Unable to close simplePs");
            }
            // not expected: there is still 1 open cursor associated with my session at this point
            try {
                conn.close();
            } catch (SQLException e) {
                System.err.println("Unable to close conn");
            }
            // as expected: at this point my session is dead and so are all the associated cursors
        }
    }
}

我发现一些Oracle文档让我觉得如果你关闭了我们的ResultSet和PreparedStatements就会关闭所有打开的游标,但是我的开放游标似乎在闲逛.请参阅此常见问题解答(http://download.oracle.com/docs/cd/B10501_01/java.920/a96654/basic.htm#1006509),其中说明“关闭结果集或语句会在数据库中释放相应的游标”.只是基于我的测试似乎没有发生,所以我必须缺乏一些基本的理解.

任何人都可以解释Oracle如何处理游标或指向一些可以启发我的文档吗?

谢谢!

最佳答案
很久以前我遇到过类似的问题.据我记忆,问题在于延迟垃圾收集.在垃圾收集器找到并释放适当的对象之前,数据库游标不会关闭.如果经常创建语句,则可能会遇到此问题.尝试不时手动调用垃圾收集器:

Runtime r = Runtime.getRuntime();
r.gc();

只是为了检查这个假设.

转载注明原文:java – 使用jdbc澄清oracle中的游标 - 代码日志