View Javadoc

1   /***
2    * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
3    */
4   package net.sourceforge.pmd.rules;
5   
6   import net.sourceforge.pmd.ast.ASTAssignmentOperator;
7   import net.sourceforge.pmd.ast.ASTClassOrInterfaceDeclaration;
8   import net.sourceforge.pmd.ast.ASTIfStatement;
9   import net.sourceforge.pmd.ast.ASTLiteral;
10  import net.sourceforge.pmd.ast.ASTMethodDeclaration;
11  import net.sourceforge.pmd.ast.ASTName;
12  import net.sourceforge.pmd.ast.ASTNullLiteral;
13  import net.sourceforge.pmd.ast.ASTPrimaryExpression;
14  import net.sourceforge.pmd.ast.ASTPrimaryPrefix;
15  import net.sourceforge.pmd.ast.ASTReferenceType;
16  import net.sourceforge.pmd.ast.ASTReturnStatement;
17  import net.sourceforge.pmd.ast.ASTStatementExpression;
18  import net.sourceforge.pmd.ast.ASTSynchronizedStatement;
19  import net.sourceforge.pmd.ast.ASTType;
20  import net.sourceforge.pmd.ast.Node;
21  
22  import java.util.ArrayList;
23  import java.util.List;
24  
25  /***
26   * void method() {
27   * if(x == null) {
28   * synchronized(this){
29   * if(x == null) {
30   * x = new | method();
31   * }
32   * }
33   * }
34   * 1.  The error is when one uses the value assigned within a synchronized
35   * section, outside of a synchronized section.
36   * if(x == null) is outside of synchronized section
37   * x = new | method();
38   * <p/>
39   * <p/>
40   * Very very specific check for double checked locking.
41   *
42   * @author CL Gilbert (dnoyeb@users.sourceforge.net)
43   */
44  public class DoubleCheckedLocking extends net.sourceforge.pmd.AbstractRule {
45  
46      public Object visit(ASTClassOrInterfaceDeclaration node, Object data) {
47          if (node.isInterface()) {
48              return data;
49          }
50          return super.visit(node, data);
51      }
52  
53      public Object visit(ASTMethodDeclaration node, Object data) {
54          if (node.getResultType().isVoid()) {
55              return super.visit(node, data);
56          }
57  
58          ASTType typeNode = (ASTType) node.getResultType().jjtGetChild(0);
59          if (typeNode.jjtGetNumChildren() == 0 || !(typeNode.jjtGetChild(0) instanceof ASTReferenceType)) {
60              return super.visit(node, data);
61          }
62  
63          List finder = new ArrayList();
64          node.findChildrenOfType(ASTReturnStatement.class, finder, true);
65          if (finder.size() != 1) {
66              return super.visit(node, data);
67          }
68          ASTReturnStatement rs = (ASTReturnStatement) finder.get(0);
69  
70          finder.clear();
71          rs.findChildrenOfType(ASTPrimaryExpression.class, finder, true);
72          ASTPrimaryExpression ape = (ASTPrimaryExpression) finder.get(0);
73          Node lastChild = ape.jjtGetChild(ape.jjtGetNumChildren() - 1);
74          String returnVariableName = null;
75          if (lastChild instanceof ASTPrimaryPrefix) {
76              returnVariableName = getNameFromPrimaryPrefix((ASTPrimaryPrefix) lastChild);
77          }
78          if (returnVariableName == null) {
79              return super.visit(node, data);
80          }
81          finder.clear();
82          node.findChildrenOfType(ASTIfStatement.class, finder, true);
83          if (finder.size() == 2) {
84              ASTIfStatement is = (ASTIfStatement) finder.get(0);
85              if (ifVerify(is, returnVariableName)) {
86                  //find synchronized
87                  finder.clear();
88                  is.findChildrenOfType(ASTSynchronizedStatement.class, finder, true);
89                  if (finder.size() == 1) {
90                      ASTSynchronizedStatement ss = (ASTSynchronizedStatement) finder.get(0);
91                      finder.clear();
92                      ss.findChildrenOfType(ASTIfStatement.class, finder, true);
93                      if (finder.size() == 1) {
94                          ASTIfStatement is2 = (ASTIfStatement) finder.get(0);
95                          if (ifVerify(is2, returnVariableName)) {
96                              finder.clear();
97                              is2.findChildrenOfType(ASTStatementExpression.class, finder, true);
98                              if (finder.size() == 1) {
99                                  ASTStatementExpression se = (ASTStatementExpression) finder.get(0);
100                                 if (se.jjtGetNumChildren() == 3) { //primaryExpression, AssignmentOperator, Expression
101                                     if (se.jjtGetChild(0) instanceof ASTPrimaryExpression) {
102                                         ASTPrimaryExpression pe = (ASTPrimaryExpression) se.jjtGetChild(0);
103                                         if (matchName(pe, returnVariableName)) {
104                                             if (se.jjtGetChild(1) instanceof ASTAssignmentOperator) {
105                                                 addViolation(data, node);
106                                             }
107                                         }
108                                     }
109                                 }
110                             }
111                         }
112                     }
113                 }
114             }
115         }
116         return super.visit(node, data);
117     }
118 
119     private boolean ifVerify(ASTIfStatement is, String varname) {
120         List finder = new ArrayList();
121         is.findChildrenOfType(ASTPrimaryExpression.class, finder, true);
122         if (finder.size() > 1) {
123             ASTPrimaryExpression apeLeft = (ASTPrimaryExpression) finder.get(0);
124             if (matchName(apeLeft, varname)) {
125                 ASTPrimaryExpression apeRight = (ASTPrimaryExpression) finder.get(1);
126                 if ((apeRight.jjtGetNumChildren() == 1) && (apeRight.jjtGetChild(0) instanceof ASTPrimaryPrefix)) {
127                     ASTPrimaryPrefix pp2 = (ASTPrimaryPrefix) apeRight.jjtGetChild(0);
128                     if ((pp2.jjtGetNumChildren() == 1) && (pp2.jjtGetChild(0) instanceof ASTLiteral)) {
129                         ASTLiteral lit = (ASTLiteral) pp2.jjtGetChild(0);
130                         if ((lit.jjtGetNumChildren() == 1) && (lit.jjtGetChild(0) instanceof ASTNullLiteral)) {
131                             return true;
132                         }
133                     }
134                 }
135             }
136         }
137         return false;
138     }
139 
140     private boolean matchName(ASTPrimaryExpression ape, String name) {
141         if ((ape.jjtGetNumChildren() == 1) && (ape.jjtGetChild(0) instanceof ASTPrimaryPrefix)) {
142             ASTPrimaryPrefix pp = (ASTPrimaryPrefix) ape.jjtGetChild(0);
143             String name2 = getNameFromPrimaryPrefix(pp);
144             if (name2 != null && name2.equals(name)) {
145                 return true;
146             }
147         }
148         return false;
149     }
150 
151     private String getNameFromPrimaryPrefix(ASTPrimaryPrefix pp) {
152         if ((pp.jjtGetNumChildren() == 1) && (pp.jjtGetChild(0) instanceof ASTName)) {
153             return ((ASTName) pp.jjtGetChild(0)).getImage();
154         }
155         return null;
156     }
157 }