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1
22 package org.jboss.aspects.dbc.condition.parser;
23
24
33 public class ExpressionParser
34 {
35 static final String  FORALL = "forall ";
36 static final String EXISTS = "exists ";
37 static final String IMPLIES = " implies ";
38 static final String JAVA = "java: ";
39 static final String IN = " in ";
40 static final String SEPARATOR = " | ";
41
42 public static Expression parseExpression(String expr)
43 {
44 return parse(expr);
45 }
46
47 private static Expression parse(String expr)
48 {
49 expr = expr.trim();
50 if (expr.startsWith(FORALL))
51 {
52 return parseForAll(expr);
53 }
54 else if (expr.startsWith(EXISTS))
55 {
56 return parseExists(expr);
57 }
58 else if (expr.indexOf(IMPLIES) > 0)
59 {
60 return parseImplies(expr);
61 }
62 else if (expr.startsWith(JAVA))
63 {
64 return parseJava(expr);
65 }
66 else
67 {
68 return parseBoolean(expr);
69 }
70 }
71
72 private static Expression parseForAll(String expr)
73 {
74 int in = expr.indexOf(IN);
75 if (in < 0) throw new RuntimeException ("forall expressions must have an 'in' clause: " + expr);
76
77 String declaration = expr.substring(FORALL.length(), in);
78
79 int sep = expr.indexOf(SEPARATOR);
80 if (sep < 0) throw new RuntimeException ("forall expressions must have a '|': " + expr);
81 String collection = expr.substring(in + IN.length(), sep);
82
83 String body = expr.substring(sep + SEPARATOR.length());
84 Expression sub = parse(body);
85 ForAllExpression forAll = new ForAllExpression(declaration, collection, sub);
86 return forAll;
87 }
88
89 private static Expression parseExists(String expr)
90 {
91 int in = expr.indexOf(IN);
92 if (in < 0) throw new RuntimeException ("exists expressions must have an 'in' clause: " + expr);
93
94 String declaration = expr.substring(EXISTS.length(), in);
95
96 int sep = expr.indexOf(SEPARATOR);
97 if (sep < 0) throw new RuntimeException ("exists expressions must have a '|': " + expr);
98 String collection = expr.substring(in + IN.length(), sep);
99
100 String body = expr.substring(sep + SEPARATOR.length());
101 Expression sub = parse(body);
102 ExistsExpression exists = new ExistsExpression(declaration, collection, sub);
103 return exists;
104 }
105
106
107 private static Expression parseImplies(String expr)
108 {
109 int impl = expr.indexOf(IMPLIES);
110 String exprA = expr.substring(0, impl);
111 String exprB = expr.substring(impl + IMPLIES.length());
112
113 if (exprA.trim().length() == 0 || exprB.trim().length() == 0)
114 {
115 throw new RuntimeException ("implies expressions must take two simple boolean expressions: " + expr);
116 }
117
118 if (exprA.endsWith(";"))
119 {
120 exprA = expr.substring(0, expr.length() - 1);
121 }
122
123 try
124 {
125 Expression condA = parse(exprA);
126 Expression condB = parse(exprB);
127
128 ImpliesExpression implies = new ImpliesExpression((BooleanExpression)condA, (BooleanExpression)condB);
129 return implies;
130 }
131 catch (ClassCastException e)
132 {
133 throw new RuntimeException ("implies expressions must take two simple boolean expressions: " + expr);
134 }
135 }
136
137 private static Expression parseJava(String expr)
138 {
139 expr = expr.substring(JAVA.length());
140 return new JavaExpression(expr);
141 }
142
143 private static Expression parseBoolean(String expr)
144 {
145 if (expr.endsWith(";"))
146 {
147 expr = expr.substring(0, expr.length() - 1);
148 }
149 return new BooleanExpression(expr);
150 }
151
152 public static void main(String [] args)
153 {
154 doit("a == b");
155 doit("a == b implies b == a");
156 doit("forall IEmployee e in getEmployees() | getRooms().contains(e.getOffice());");
157 doit("exists IEmployee e in getEmployees() | !getRooms().contains(e.getOffice())");
158 doit("forall IEmployee e1 in getEmployees() | forall IEmployee e2 in getEmployees() | (e1 != e2) implies e1.getOffice() != e2.getOffice()");
159 doit("java: for (int i = 0){i > 0;}");
160 }
161
162 public static void doit(String str)
163 {
164 System.out.println(str);
165 System.out.println();
166 Expression expr = ExpressionParser.parseExpression(str);
167 BeanshellGenerator gen = new BeanshellGenerator(expr);
168 System.out.println(gen.createBeanshellCode());
169 System.out.println("-----------------------");
170 }
171 }
172 |
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