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Java > Open Source Codes > org > apache > cayenne > access > jdbc > EJBQLOrderByTranslator


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19 package org.apache.cayenne.access.jdbc;
20
21 import org.apache.cayenne.ejbql.EJBQLBaseVisitor;
22 import org.apache.cayenne.ejbql.EJBQLException;
23 import org.apache.cayenne.ejbql.EJBQLExpression;
24 import org.apache.cayenne.ejbql.EJBQLExpressionVisitor;
25 import org.apache.cayenne.ejbql.parser.EJBQLPath;
26
27 /**
28  * @since 3.0
29  * @author Andrus Adamchik
30  */
31 class EJBQLOrderByTranslator extends EJBQLBaseVisitor {
32
33     private EJBQLTranslationContext context;
34     private int itemCount;
35
36     EJBQLOrderByTranslator(EJBQLTranslationContext context) {
37         this.context = context;
38     }
39
40     public boolean visitOrderByItem(EJBQLExpression expression) {
41         if (itemCount++ > 0) {
42             context.append(',');
43         }
44
45         return true;
46     }
47
48     public boolean visitDescending(EJBQLExpression expression) {
49         context.append(" DESC");
50         return true;
51     }
52
53     public boolean visitPath(EJBQLPath expression, int finishedChildIndex) {
54
55         EJBQLExpressionVisitor childVisitor = new EJBQLPathTranslator(context) {
56
57             protected void appendMultiColumnPath(EJBQLMultiColumnOperand operand) {
58                 throw new EJBQLException("Can't order on multi-column paths or objects");
59             }
60         };
61         expression.visit(childVisitor);
62         return false;
63     }
64 }
65
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