JDBC Oracle结果集空指针异常

Question

I have a multi threaded program which connects to a oracle database.

The first thread executes a "big" query and loads the objects in to a LinkedBlockingQueue. There are around 200,000 objects.

The second thread polls this list, and for each object, it runs 14 other queries, updating the object parameters. Then I connect to another database, one final time, get corresponding object for this current object, create a hybrid object containing these two objects and sends it to third thread.

I am using a single statement and multiple result sets for each one of these 14 queries.

    stat=predefinedobject.getConnection().createStatement();  
    ResultSet rs = null;
    ResultSet rs1 = null;
    ResultSet rs2 = null;
    ResultSet rs3 = null;
          .
          .
    rs=stat.executeQuery(Query1);
    while(rs.next()) {
        object1.setParameter1(rs.getString(5));
    }
    SqlUtils.closeResultSet(rs);

    rs1=stat.executeQuery(Query2);
    while(rs1.next()) {
        object1.setParameter2(rs1.getString(5));
    }
    SqlUtils.closeResultSet(rs1);
           .
           .
           .
    SqlUtils.closeResultSet(rs14);
    SqlUtils.closeResultSet(stat);

I am getting the null pointer exception after some time.

java.lang.NullPointerException
at oracle.jdbc.driver.T4C8Oall.getNumRows(T4C8Oall.java:876)
at oracle.jdbc.driver.T4CStatement.executeForDescribe(T4CStatement.java:825)
at oracle.jdbc.driver.OracleStatement.executeMaybeDescribe(OracleStatement.java:1049)
at oracle.jdbc.driver.T4CStatement.executeMaybeDescribe(T4CStatement.java:845)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1154)
at oracle.jdbc.driver.OracleStatement.executeQuery(OracleStatement.java:1313)

Answer 1

Double check your sql query strings , it seems you concatenate the query but missing some space in it.

For example;

String sql="select"+MYCOULUM+" form MYTABLE"

will produce the following string

selectMYCOULUM form MYTABLE

and executing such query will result this error for oracle jdbc driver

Answer 2

The javadoc says - By default, only one ResultSet object per Statement object can be open at the same time. Therefore, if the reading of one ResultSet object is interleaved with the reading of another, each must have been generated by different Statement objects. All execution methods in the Statement interface implicitly close a statment's current ResultSet object if an open one exists.

So may be try to create a new Statement object each time you want to query the database

Answer 3

In my case, I've used upper case CALL instead of lower case call to call stored proc.

For example, { ?= CALL proc_name(?) } is giving the same error. Once I change to { ?= call proc_name(?) } it is working