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Java > Open Source Codes > org > objectstyle > cayenne > exp > ASTCompiler


1 /* ====================================================================
2  *
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24  * and hosted on ObjectStyle Group web site (http://objectstyle.org/)."
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56 package org.objectstyle.cayenne.exp;
57
58 import java.util.HashMap JavaDoc;
59 import java.util.Map JavaDoc;
60
61 /**
62  * A compiler for Cayenne Expressions.
63  *
64  * @since 1.0.6
65  * @author Andrei Adamchik
66  */
67 class ASTCompiler {
68
69     /**
70      * Produces a chain of ASTNodes, returning the starting node that can be used
71      * to evaluate expressions.
72      */
73     static ASTNode compile(Expression expression) throws ExpressionException {
74         ExpressionParser handler = new ExpressionParser();
75         expression.traverse(handler);
76         return handler.finishParsing(expression);
77     }
78
79     static final class ExpressionParser extends TraversalHelper {
80         // TODO - for big expressions we may remove cached AST from the map
81 // once a node and all its children are procesed, to keep the map as small
82 // as possible during compilation... Though most data expressions are rather small,
83 // and have from a few to a few dozen nodes...
84
85         ASTNode currentNode;
86         ASTNode startNode;
87         Map JavaDoc astMap = new HashMap JavaDoc();
88
89         ASTNode finishParsing(Expression expression) {
90             // must add the top node to the tree. since "finishedChild"
91 // is never invoked for the top node as child.
92 processNode((ASTNode) astMap.get(expression));
93
94             return startNode;
95         }
96
97         public void startNode(Expression node, Expression parentNode) {
98             // create an ASTNode and store it so that children could link
99 // to it.
100 ASTNode parentAST = (ASTNode) astMap.get(parentNode);
101             astMap.put(node, ASTNode.buildExpressionNode(node, parentAST));
102         }
103
104         public void finishedChild(
105             Expression node,
106             int childIndex,
107             boolean hasMoreChildren) {
108
109             // skip children of precompiled nodes, such as
110 // OBJ_PATH, LIST, and varieties of LIKE
111 int type = node.getType();
112             if (type == Expression.OBJ_PATH
113                 || type == Expression.LIST
114                 || (childIndex == 1
115                     && (type == Expression.LIKE
116                         || type == Expression.LIKE_IGNORE_CASE
117                         || type == Expression.NOT_LIKE
118                         || type == Expression.NOT_LIKE_IGNORE_CASE))) {
119                 return;
120             }
121
122             // add expression to the chain
123 Object JavaDoc child = node.getOperand(childIndex);
124
125             // unless child is not an expression, it must be cached already
126 ASTNode newAST;
127             if (child instanceof Expression) {
128                 newAST = (ASTNode) astMap.get(child);
129             }
130             else {
131                 ASTNode parentAST = (ASTNode) astMap.get(node);
132                 newAST = ASTNode.buildObjectNode(child, parentAST);
133             }
134
135             processNode(newAST);
136         }
137
138         void processNode(ASTNode newAST) {
139             if (startNode == null) {
140                 startNode = newAST;
141                 currentNode = newAST;
142             }
143             else {
144                 currentNode.setNextNode(newAST);
145                 currentNode = newAST;
146             }
147         }
148     }
149 }
150
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