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java- ClassCastException- BigInt cannot be cast to Long

General Tech Bugs & Fixes

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User

( 6 months ago )

 

I have two columns in my table are which is BigInt data type (NODEID and ULNODEID) and I want to keep it that way. I am using MYSQL workbench 8.0 for these table.

I want to get the value of my nodeid using the function below:

 public long get_urlnodeid(long nodeID) {
        try {


                String sql = "select NODEID from urllink where ULNODEID="+nodeID;
            if (em == null) {
                throw new Exception("could not found URL object.");
            }

            return (long) em.createNativeQuery(sql).getSingleResult();


        } catch (Exception e) {

            msg = CoreUtil.wrapMsg(CoreUtil.FUNC_ERROR,
                    this.getClass().getName(), "get", e.getMessage());

        }
        return 0;
    }

It throws an exception saying Big Integer cannot be cast to java.lang.Long

Is there a way I can retrieve the value while keeping it in long?

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User

( 6 months ago )

Just look at the Java doc for BigInteger:

public long longValue()

Converts this BigInteger to a long. This conversion is analogous to a narrowing primitive conversion from long to int as defined in section 5.1.3 of The Java™ Language Specification: if this BigInteger is too big to fit in a long, only the low-order 64 bits are returned. Note that this conversion can lose information about the overall magnitude of the BigInteger value as well as return a result with the opposite sign.

So you'd want something like this:

return ((BigInteger)em.createNativeQuery(sql).getSingleResult()).longValue();

I would recommend adding some type checking.

--

Another option, if you have full control of your application, and you expect values that go beyond the range of long, is to have your method return BigInteger instead of long:

public BigInteger get_urlnodeid(long nodeID) {

And:

return (BigInteger) em.createNativeQuery(sql).getSingleResult();

Of course then the rest of your application that calls this method has to work with BigInteger as well.

Please be aware that using BigInteger instead of long is much less performant, so only use this if performance is not an issue or if you are absolutely sure that values will be so big that this is absolutely necessary.

what's your interest


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