如何使用Java代码比较VARCHAR数据类型以确保数据库中的数据相同

Question

How do I compare the value in two different databases with the same data in the columns because of data migration. I am running jUnit Tests and the values are not passing the test as the same. What am I doing wrong? Right know I have the sourceDB and the target database set to the same database, ie they are they same thing. I did this because I want to be sure the connection was correct throughout the process and narrow down any problems to syntax errors. The value in the rows of the name column is; Initiative Management, Bugs & Enhancements, Hardware & Software Requests.

public class DemandTypeCopier {

    public static String QUERY_CREATECOPY = "select name from tr_demandtype where name=?";

}

public void testQUERY_CREATECOPY() throws Exception{

    UnitTestHelper helper = new UnitTestHelper();
    Connection con = helper.getConnection(helper.sourceDBUrl);
    Connection conTarget = helper.getConnection(helper.targetDBUrl);
    String x = "Initiative management";

    PreparedStatement stmt = con.prepareStatement(DemandTypeCopier.QUERY_CREATECOPY);
    stmt.setString(1, x);
    ResultSet sourceVal = stmt.executeQuery();

    stmt = conTarget.prepareStatement(DemandTypeCopier.QUERY_CREATECOPY);
    stmt.setString(1, x);
    ResultSet targetVal = stmt.executeQuery();

    assertTrue(helper.resultSetsEqual(sourceVal,targetVal));

}

public boolean resultSetsEqual (ResultSet source, ResultSet target) throws SQLException{
    while(source.next())
    {
            target.next();
            ResultSetMetaData metadata = source.getMetaData();
            int count = metadata.getColumnCount();
            for (int i =1; i<=count; i++)
            {
               if(source.getObject(i) != target.getObject(i))
               {
              return false;
               }
            }
    }
    return true;
}

Answer 1

The problem is that when comparing the data, you are testing object identity instead of equality.

source.getObject(i) != target.getObject(i)

The above will test if the objects returned from both resultsets are the same which will not be true in most (all?) cases. What you really want to do is test for equality:

source.getObject(i).equals(target.getObject(i))

Note that the above would throw a NullPointerException if source.getObject(i) returns null, so unless null values are not allowed for any of the columns in the database, you would need to add code to handle null values.

Add an ORDER BY clause to your query, otherwise the order of the returned results is not guaranteed.

Check the result of target.next() so that you correctly handle the case when the size of the two resultsets are not equal.