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1 package com.tirsen.nanning.contract;
2
3 import java.text.MessageFormat  ;
4 import java.util.ArrayList ;
5 import java.util.List ;
6 import java.util.ListIterator ;
7 import java.util.Map ;
8 import java.util.regex.Matcher ;
9 import java.util.regex.Pattern ;
10
11 import com.tirsen.nanning.Invocation;
12 import com.tirsen.nanning.MethodInterceptor;
13 import com.tirsen.nanning.attribute.Attributes;
14 import ognl.MethodFailedException;
15 import ognl.Ognl;
16 import org.apache.commons.logging.Log;
17 import org.apache.commons.logging.LogFactory;
18
19
27 public class ContractInterceptor implements MethodInterceptor {
28 private static final Log logger = LogFactory.getLog(ContractInterceptor.class);
29 private static final Pattern oldPattern =
30 Pattern.compile("(.*)\\{old (.*?)}(.*)");
31
32
35 private ThreadLocal checkContracts = new ThreadLocal ();
36
37 public Object invoke(Invocation invocation) throws Throwable {
38 String ensures = Attributes.getAttribute(invocation.getMethod(), "ensures");
39 String requires = Attributes.getAttribute(invocation.getMethod(), "requires");
40 String invariant = Attributes.getAttribute(invocation.getMethod().getDeclaringClass(), "invariant");
41
42 StringBuffer parsedEnsure = null;
43 List oldValues = null;
44
45 if (checkContracts.get() == null) {
46 assertExpressionTrue(invocation, requires,
47 "precondition violated: {0}");
48
49 if (ensures != null) {
51 oldValues = new ArrayList ();
52 parsedEnsure = new StringBuffer ();
53 Matcher matcher = oldPattern.matcher(ensures);
54 while (matcher.matches()) {
55 String head = matcher.group(1);
56 String old = matcher.group(2);
57 String tail = matcher.group(3);
58 oldValues.add(executeExpression(invocation, old));
59 String oldRef = "#" + getOldReference(oldValues.size() - 1);
60 parsedEnsure.append(head + oldRef + tail);
61 matcher = oldPattern.matcher(tail);
62 }
63 if (oldValues.size() == 0) {
65 parsedEnsure.append(ensures);
66 }
67 }
68 }
69
70 Object result = invocation.invokeNext();
71
72 if (checkContracts.get() == null) {
73
74 if (parsedEnsure != null) {
76 Map context = createContext(invocation);
77 for (ListIterator iterator = oldValues.listIterator(); iterator.hasNext();) {
78 Object oldValue = iterator.next();
79 context.put(getOldReference(iterator.previousIndex()), oldValue);
80 }
81
82 assertExpressionTrue(parsedEnsure.toString(),
83 invocation.getProxy(), context, "postcondition violated: " + ensures);
84 }
85
86 assertExpressionTrue(invocation, invariant, "invariant violated: {0}");
87 }
88
89 return result;
90 }
91
92 private static String getOldReference(int i) {
93 return "old" + i;
94 }
95
96 private Object executeExpression(Invocation invocation, String expression) {
97 Map context = createContext(invocation);
98 try {
99 return executeExpression(expression, invocation.getProxy(), context);
100 } catch (Exception e) {
101 throw new RuntimeException ("Could not execute: " + expression, e);
102 }
103 }
104
105 private void assertExpressionTrue(Invocation invocation, String expression, String message) {
106 if (expression != null) {
107 Map context = createContext(invocation);
108 assertExpressionTrue(expression, invocation.getProxy(), context, MessageFormat.format(message, new Object []{expression}));
109 }
110 }
111
112 private static Map createContext(Invocation invocation) {
113 Map variables = Ognl.createDefaultContext(invocation.getProxy());
114 variables.put("this", invocation.getProxy());
115 Object [] args = invocation.getArgs();
116 if (args != null) {
117 for (int i = 0; i < args.length; i++) {
118 Object arg = args[i];
119 variables.put("arg" + i, arg);
120 }
121 }
122 return variables;
123 }
124
125 private void assertExpressionTrue(String expression, Object root, Map context, String message) {
126 if (checkContracts.get() == null) {
128 checkContracts.set(checkContracts);
129 try {
130 boolean result;
131 Boolean aBoolean = (Boolean ) executeExpression(expression, root, context);
132 result = aBoolean.booleanValue();
133 if (!result) {
134 throw new AssertionError (message);
135 }
136 } catch (MethodFailedException e) {
137 if (e.getReason() instanceof Error ) {
138 throw (Error ) e.getReason();
139 } else {
140 logger.error("Could not execute expression: " + expression);
141 throw new AssertionError ("Could not execute expression: " + expression);
142 }
143 } catch (Exception e) {
144 logger.error("Could not execute expression: " + expression);
145 throw new AssertionError ("Could not execute expression: " + expression);
146 } finally {
147 checkContracts.set(null);
148 }
149 }
150 }
151
152 private static Object executeExpression(String expression, Object root, Map context) throws Exception {
153 return Ognl.getValue(Ognl.parseExpression(expression), context, root);
154 }
155 }
156
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