Sample2


1   package samples.interceptor;
2   
3   import java.lang.reflect.Field  ;
4   
5   import alt.jiapi.InstrumentationContext;
6   import alt.jiapi.InstrumentationDescriptor;
7   import alt.jiapi.reflect.Loader;
8   import alt.jiapi.reflect.JiapiClass;
9   import alt.jiapi.util.Bootstrapper;
10  import alt.jiapi.util.InstrumentingClassLoader;
11  
12  import alt.jiapi.interceptor.*;
13  
14  /**
15   * Sample2 demonstrates how to intercept field accesses
16   * made.
17   * One is free to modify method call parameters / return value at will, as 
18   * long as their type matches methods signature.
19   */
20  public class Sample2 implements AccessAdvisor, FieldHandler {
21      public static void main(String   args[]) throws Exception   {
22          new Sample2();
23      }
24      
25      public Sample2() throws Exception   {
26          // Configure:
27          InstrumentationContext ctx = new InstrumentationContext();
28          InstrumentationDescriptor id = new InstrumentationDescriptor();
29          id.addInclusionRule("samples.*");
30          ctx.addInstrumentationDescriptor(id);
31          
32          // Associate interceptor with descriptor
33          // Set resolution to 'samples*', which means that interceptor applies
34          // its work only on fields which start with 'samples'
35  
36          // FieldInterceptor uses AccessAdvisor
37          FieldInterceptor fi = new FieldInterceptor(id, "samples*",this);
38          // FieldInterceptor2 uses reflection/FieldHandler. This is obsolete.
39          // Performance is roughly 100 times slower
40          //FieldInterceptor2 fi2 = new FieldInterceptor2(id, "samples*Bar*", this);
41  
42          // Launch ITest
43          Bootstrapper.launch("samples.Foo", null, ctx, 
44                              InstrumentingClassLoader.createClassLoader(ctx));
45      }
46         
47  
48      /**
49       * FieldAdvisor
50       * 
51       * @param o target instance. If this is null, target Method is 
52       *          static
53       * @param m Method, that this handler is supposed to invoke
54       * @param args Arguments, that are suitable to be passed to
55       *          reflective method.
56       */
57      public Object   get(Object   o, String   name, Object   value) {
58      System.out.println("   Getting field " + name + ": ");
59  
60           if (value instanceof String  ) {
61               value = ((String  )value).toUpperCase();
62           }
63           else if (value instanceof Integer  ) {
64               value = new Integer  (100);
65           }
66  
67          return value; 
68      }
69  
70  
71      /**
72       * FieldAdvisor interface
73       * 
74       * @param o target instance. If this is null, target Method is 
75       *          static
76       * @param m Method, that this handler is supposed to invoke
77       * @param args Arguments, that are suitable to be passed to
78       *          reflective method.
79       */
80      public Object   set(Object   o, String   name, Object   value) {
81          System.out.println("   Setting field " + name + ": " + value);
82          return value;
83      }
84  
85  
86      // FieldHandler interface -- Used with FieldInterceptor2
87      public void setField(Object   target, Field   field, Object   value) throws Exception   {
88      //System.out.println("Setting field");
89          field.set(target, value);
90      }
91      
92      public Object   getField(Object   target, Field   field) throws Exception   {
93      System.out.println("getting");
94          return field.get(target);
95      }
96  }
97
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