[JDBC/Oracle]设置Statement.setQueryTimeout(seconds)并不好用 原因：环境问题

对比实验：https://www.cnblogs.com/xiandedanteng/p/11960320.html

注：setQueryTimeout语句还是好用的，但有些环境不支持，下文是在单位虚拟机上的Oracle发生的事情，而setQueryTimeout语句在我家机器上的Oracle是支持的，详情请见。

本以为,遇到其它session导致行锁发生的情况,设置Statement.setQueryTimeout(seconds)就好了,至少不会让程序等待太长时间,但是事与愿违,我发现无论是设置自动Commit还是手动commit,setQueryTimeout都不好用.

似乎有人也遇到了和我一样的情况:https://community.oracle.com/thread/552257

我的数据库是: select * from v$version;

Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
PL/SQL Release 12.2.0.1.0 - Production
"CORE 12.2.0.1.0 Production"
TNS for Linux: Version 12.2.0.1.0 - Production
NLSRTL Version 12.2.0.1.0 - Production

两端设置超时无效的程序如下:

package tablelock;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

import org.apache.log4j.Logger;

public class Deleter {
    private static Logger log = Logger.getLogger(Deleter.class);

    public void doDelete() {
        Connection conn = null;
        Statement stmt = null;

        try{
            Class.forName(DBParam.Driver).newInstance();
            conn = DriverManager.getConnection(DBParam.DbUrl, DBParam.User, DBParam.Pswd);
            conn.setAutoCommit(false);
            stmt = conn.createStatement();
            stmt.setQueryTimeout(1);// It dosen't work

            String sql="delete from TestTB17 where id=2";
            int deleted=stmt.executeUpdate(sql);

            log.info("Deleter deleted "+deleted+" records.");

            conn.commit();
            log.info("committed.");
        } catch (Exception e) {
            e.printStackTrace();
            //System.out.print(e.getMessage());
        } finally {
            try {
                stmt.close();
                conn.close();
            } catch (SQLException e) {
                System.out.print("Can't close stmt/conn because of " + e.getMessage());
            }
        }
    }

    public static void main(String[] args) {
        Deleter d=new Deleter();
        d.doDelete();
    }
}

package tablelock;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

import org.apache.log4j.Logger;

public class Deleter2 {
    private static Logger log = Logger.getLogger(Deleter2.class);

    public void doDelete() {
        Connection conn = null;
        Statement stmt = null;

        try{
            Class.forName(DBParam.Driver).newInstance();
            conn = DriverManager.getConnection(DBParam.DbUrl, DBParam.User, DBParam.Pswd);
            stmt = conn.createStatement();
            stmt.setQueryTimeout(1);// It dosen't work

            String sql="delete from TestTB17 where id=3";
            int deleted=stmt.executeUpdate(sql);

            log.info("Deleter deleted "+deleted+" records.");
        } catch (Exception e) {
            e.printStackTrace();
            //System.out.print(e.getMessage());
        } finally {
            try {
                stmt.close();
                conn.close();
            } catch (SQLException e) {
                System.out.print("Can't close stmt/conn because of " + e.getMessage());
            }
        }
    }

    public static void main(String[] args) {
        Deleter2 d=new Deleter2();
        d.doDelete();
    }
}

在以下程序的log.info处设置断点就能使上面两个Deleter执行不下去:

package tablelock;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

import org.apache.log4j.Logger;

public class Selecter {
    private static Logger log = Logger.getLogger(Selecter.class);

    public void doSelectfor() {
        Connection conn = null;
        Statement stmt = null;

        try{
            Class.forName(DBParam.Driver).newInstance();
            conn = DriverManager.getConnection(DBParam.DbUrl, DBParam.User, DBParam.Pswd);
            conn.setAutoCommit(false);
            stmt = conn.createStatement();

            String sql="select * from TestTB17 for update";
            stmt.executeUpdate(sql);

            log.info("Will block other session before commit/rollback.");

            conn.commit();
            log.info("committed.");
        } catch (Exception e) {
            System.out.print(e.getMessage());
        } finally {
            try {
                stmt.close();
                conn.close();
            } catch (SQLException e) {
                System.out.print("Can't close stmt/conn because of " + e.getMessage());
            }
        }
    }

    public static void main(String[] args) {
        Selecter d=new Selecter();
        d.doSelectfor();
    }
}

具体是何原因还有待查.

--To be continued-- 2019-11-29 10:47