我正在尝试运行多个相互构建的MySQL查询：即每行中一个元素的字段值用作另一个查询的输入。
我最终收到以下错误：
java.sql.SQLException: Streaming result set com.mysql.jdbc.RowDataDynamic@174cc1f is still active. No statements may be issued when any streaming result sets are open and in use on a given connection. Ensure that you have called .close() on any active streaming result sets before attempting more queries.
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:914)
at com.mysql.jdbc.MysqlIO.checkForOutstandingStreamingData(MysqlIO.java:2074)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1484)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1665)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3170)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3099)
at com.mysql.jdbc.Statement.executeQuery(Statement.java:1169)
at Stats.readInterfaces(Stats.java:105)
at Stats.connect(Stats.java:63)
at automateExport.main(automateExport.java:15)
我在查询的每个.close()和ResultSet之后调用了Statement。我想我们不能同时打开多个结果集。有没有办法解决这个问题？
以下是相关代码：
public class Stats {
public static int UTC = 0;
public String interfaceId = "no value";
public String rId = "no value";
public String NL = System.getProperty("line.separator");
public String CSV = ",";
public static String startTime,endTime,performanceTable =null;
public static int outputType = 1;
public String pTable = "('2010-7-13 00:00')";
public String start = "('2010-7-13 09:00')";
public String end = "('2010-7-13 17:00')";
Connection conn;
Statement stmtRouter, stmtInterface, stmtTime, stmtD;
String query;
ResultSet rsRouter, rsInterface, rsD, rsTime;
public Connection connect(String db_connect_str,String db_userid, String db_password) {
String routerName,routerId = null, routerNetwork = null;
// inputfile - csv
try {
// to bifurcate heap memory error
Class.forName("com.mysql.jdbc.Driver").newInstance();
conn = DriverManager.getConnection(db_connect_str,db_userid, db_password);
stmtRouter = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
java.sql.ResultSet.CONCUR_READ_ONLY);
stmtRouter.setFetchSize(Integer.MIN_VALUE);
query = "Select r.name,r.rid,r.network FROM router AS r Where r.network = 'ITPN'";
String append = null;
// writing to file
performanceTable = readTime(pTable);
startTime = readTime(start);
endTime = readTime(end);
rsRouter = stmtRouter.executeQuery(query);
while (rsRouter.next()) {
routerName = rsRouter.getString(1);
System.out.println(routerName);
// routerId = rsRouter.getString("rid");
// routerNetwork = rsRouter.getString("network");
append = routerName+CSV+routerId+CSV+routerNetwork;
readInterfaces(routerId,startTime,endTime,performanceTable, append);
}
stmtRouter.close() ;
rsRouter.close();
// output(2,input);
// output(outputType , input);
} catch(Exception e) {
e.printStackTrace();
conn = null;
}
return conn;
}
private String readTime(String time) throws SQLException {
stmtTime = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
java.sql.ResultSet.CONCUR_READ_ONLY);
stmtTime.setFetchSize(Integer.MIN_VALUE);
query = "Select unix_timestamp"+time;
rsTime = stmtTime.executeQuery(query);
String unixTime = null;
while(rsTime.next()){
unixTime = rsTime.getString(1);
System.out.println(unixTime);
}
rsTime.close();
stmtTime.close();
return unixTime;
}
private void readInterfaces(String routerId, String startTime, String endTime, String performanceTable, String append) throws SQLException, IOException {
String interfaceId, iDescp, iStatus = null;
String dtime, ingress, egress = null;
stmtInterface = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
java.sql.ResultSet.CONCUR_READ_ONLY);
stmtInterface.setFetchSize(Integer.MIN_VALUE);
stmtD = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
java.sql.ResultSet.CONCUR_READ_ONLY);
stmtD.setFetchSize(Integer.MIN_VALUE);
query = " Select i.id,i.description, i.status from interface as i Where i.rid = " + routerId +" And i.status = 'active'";
rsInterface = stmtInterface.executeQuery(query);
String input = "inputData.txt";
BufferedWriter fw = new BufferedWriter(new FileWriter(input));
stmtInterface.close();
while(rsInterface.next()){
interfaceId = rsInterface.getString("id");
iDescp = rsInterface.getString("description");
iStatus = rsInterface.getString("status");
if(!iStatus.equals("active")){
/* performance table query*/
query = " Select d.dtime,d.ifInOctets, d.ifOutOctets from "+performanceTable+"_1_60" +" AS d Where d.id = " +
interfaceId + "AND dtime BETWEEN " +startTime+ " AND "+ endTime + " Order By d.id";
rsD = stmtD.executeQuery(query);
while(rsD.next()){
dtime = rsD.getString("dtime");
ingress = rsD.getString("ifInOctets");
egress = rsD.getString("ifOutOctets");
fw.write(append + CSV + interfaceId+CSV+iDescp+CSV+dtime+CSV+ingress+CSV+egress+NL);
}// end of while
rsD.close();
stmtD.close();
}
}
fw.close();
// rsInterface.close() ;
// stmtInterface.close();
}
}
答案 0 :(得分：5)
正如错误所示，当您打开流式结果集时，无法通过同一连接发出其他查询。相关文档为here。
因此，显而易见的解决方案是不使用流式结果集来进行驱动查询。这样做的缺点是它会占用更多内存。代码顶部的相当模糊的注释意味着可能有人已经尝试过并且存在内存问题。
无论如何，有一个更好的解决方案。这是过度程序化的典型例子。您正在使用可以由数据库引擎更好地处理的代码。您可以使用连接将这些查询组合成一个查询，而不是执行相互驱动的单表查询：
Select r.name,r.rid,r.network,i.id,i.description, i.status
FROM router AS r JOIN interface as i ON i.rid = r.rid
Where r.network = 'ITPN'
AND i.status='active'
然后，您有第三个“嵌套”查询，您可以将其与其他联接合并。我想会是：
Select r.name,r.rid,r.network,i.id,i.description, i.status,d.dtime,d.ifInOctets, d.ifOutOctets
FROM router AS r JOIN interface as i ON i.rid = r.rid
JOIN <performanceTable>_1_60 as d ON d.id = i.id
Where r.network = 'ITPN'
AND i.status='active'
AND dtime BETWEEN <startTime> AND <endTime>
Order By d.id
您可能不需要最终选择列表中的所有列，但我没有仔细查看您的代码以查看实际使用的内容。
答案 1 :(得分：1)
每个连接不能打开多个结果集。我相信这是失败的原因：
在关闭路由器结果集之前调用readInterfaces（routerId，startTime，endTime，performanceTable，append）（打开新结果集）：
readInterfaces(routerId,startTime,endTime,performanceTable, append);
}
stmtRouter.close() ;
rsRouter.close();
我会在调用readInterfaces（...）之前移动close语句。 我也会以相反的顺序关闭结果集和语句（结果集首先）。
答案 2 :(得分：0)
在使用ResultSet（函数readInterfaces）之前，绝对不应该关闭Statement对象。
rsInterface = stmtInterface.executeQuery(query);
String input = "inputData.txt";
BufferedWriter fw = new BufferedWriter(new FileWriter(input));
stmtInterface.close(); // Don't do this!!! It should be when you are done with rsInterface)
while(rsInterface.next()){
答案 3 :(得分：-1)
Connection对象不应该一次拥有多个ResultSet对象。
创建ResultSet和Statement个对象后，每个对象都必须明确关闭，
resultSet.close()
statement.close()