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Java > Open Source Codes > bsh > TargetError


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33
34
35 package bsh;
36
37 import java.lang.reflect.InvocationTargetException JavaDoc;
38
39 import java.io.PrintStream JavaDoc;
40
41 /**
42     TargetError is an EvalError that wraps an exception thrown by the script
43     (or by code called from the script). TargetErrors indicate exceptions
44     which can be caught within the script itself, whereas a general EvalError
45     indicates that the script cannot be evaluated further for some reason.
46     
47     If the exception is caught within the script it is automatically unwrapped,
48     so the code looks like normal Java code. If the TargetError is thrown
49     from the eval() or interpreter.eval() method it may be caught and unwrapped
50     to determine what exception was thrown.
51 */
52 public class TargetError extends EvalError
53 {
54     Throwable JavaDoc target;
55     boolean inNativeCode;
56
57     public TargetError(
58         String JavaDoc msg, Throwable JavaDoc t, SimpleNode node, CallStack callstack,
59         boolean inNativeCode )
60     {
61         super( msg, node, callstack );
62         target = t;
63         this.inNativeCode = inNativeCode;
64     }
65
66     public TargetError( Throwable JavaDoc t, SimpleNode node, CallStack callstack )
67     {
68         this("TargetError", t, node, callstack, false);
69     }
70
71     public Throwable JavaDoc getTarget()
72     {
73         // check for easy mistake
74 if(target instanceof InvocationTargetException JavaDoc)
75             return((InvocationTargetException JavaDoc)target).getTargetException();
76         else
77             return target;
78     }
79
80     public String JavaDoc toString()
81     {
82         return super.toString()
83             + "\nTarget exception: " +
84             printTargetError( target );
85     }
86
87     public void printStackTrace() {
88         printStackTrace( false, System.err );
89     }
90
91     public void printStackTrace( PrintStream JavaDoc out ) {
92         printStackTrace( false, out );
93     }
94
95     public void printStackTrace( boolean debug, PrintStream JavaDoc out ) {
96         if ( debug ) {
97             super.printStackTrace( out );
98             out.println("--- Target Stack Trace ---");
99         }
100         target.printStackTrace( out );
101     }
102
103     /**
104         Generate a printable string showing the wrapped target exception.
105         If the proxy mechanism is available, allow the extended print to
106         check for UndeclaredThrowableException and print that embedded error.
107     */
108     public String JavaDoc printTargetError( Throwable JavaDoc t )
109     {
110         String JavaDoc s = target.toString();
111
112         if ( Capabilities.canGenerateInterfaces() )
113             s += "\n" + xPrintTargetError( t );
114
115         return s;
116     }
117
118     /**
119         Extended form of print target error.
120         This indirection is used to print UndeclaredThrowableExceptions
121         which are possible when the proxy mechanism is available.
122
123         We are shielded from compile problems by using a bsh script.
124         This is acceptable here because we're not in a critical path...
125         Otherwise we'd need yet another dynamically loaded module just for this.
126     */
127     public String JavaDoc xPrintTargetError( Throwable JavaDoc t )
128     {
129         String JavaDoc getTarget =
130             "import java.lang.reflect.UndeclaredThrowableException;"+
131             "String result=\"\";"+
132             "while ( target instanceof UndeclaredThrowableException ) {"+
133             " target=target.getUndeclaredThrowable(); " +
134             " result+=\"Nested: \"+target.toString();" +
135             "}"+
136             "return result;";
137         Interpreter i = new Interpreter();
138         try {
139             i.set("target", t);
140             return (String JavaDoc)i.eval( getTarget );
141         } catch ( EvalError e ) {
142             throw new InterpreterError("xprintarget: "+e.toString() );
143         }
144     }
145
146     /**
147         Return true if the TargetError was generated from native code.
148         e.g. if the script called into a compiled java class which threw
149         the excpetion. We distinguish so that we can print the stack trace
150         for the native code case... the stack trace would not be useful if
151         the exception was generated by the script. e.g. if the script
152         explicitly threw an exception... (the stack trace would simply point
153         to the bsh internals which generated the exception).
154     */
155     public boolean inNativeCode() {
156         return inNativeCode;
157     }
158 }
159
160
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