ExceptionWithContext.java revision 579d7739c53a2707ad711a2d2cae46d7d782f061 
1/*
2 * Copyright (C) 2007 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.dx.util;
18
19import java.io.PrintStream;
20import java.io.PrintWriter;
21
22/**
23 * Exception which carries around structured context.
24 */
25public class ExceptionWithContext
26        extends RuntimeException {
27    /** {@code non-null;} human-oriented context of the exception */
28    private StringBuffer context;
29
30    /**
31     * Augments the given exception with the given context, and return the
32     * result. The result is either the given exception if it was an
33     * {@link ExceptionWithContext}, or a newly-constructed exception if it
34     * was not.
35     *
36     * @param ex {@code non-null;} the exception to augment
37     * @param str {@code non-null;} context to add
38     * @return {@code non-null;} an appropriate instance
39     */
40    public static ExceptionWithContext withContext(Throwable ex, String str) {
41        ExceptionWithContext ewc;
42
43        if (ex instanceof ExceptionWithContext) {
44            ewc = (ExceptionWithContext) ex;
45        } else {
46            ewc = new ExceptionWithContext(ex);
47        }
48
49        ewc.addContext(str);
50        return ewc;
51    }
52
53    /**
54     * Constructs an instance.
55     *
56     * @param message human-oriented message
57     */
58    public ExceptionWithContext(String message) {
59        this(message, null);
60    }
61
62    /**
63     * Constructs an instance.
64     *
65     * @param cause {@code null-ok;} exception that caused this one
66     */
67    public ExceptionWithContext(Throwable cause) {
68        this(null, cause);
69    }
70
71    /**
72     * Constructs an instance.
73     *
74     * @param message human-oriented message
75     * @param cause {@code null-ok;} exception that caused this one
76     */
77    public ExceptionWithContext(String message, Throwable cause) {
78        super((message != null) ? message :
79              (cause != null) ? cause.getMessage() : null,
80              cause);
81
82        if (cause instanceof ExceptionWithContext) {
83            String ctx = ((ExceptionWithContext) cause).context.toString();
84            context = new StringBuffer(ctx.length() + 200);
85            context.append(ctx);
86        } else {
87            context = new StringBuffer(200);
88        }
89    }
90
91    /** {@inheritDoc} */
92    @Override
93    public void printStackTrace(PrintStream out) {
94        super.printStackTrace(out);
95        out.println(context);
96    }
97
98    /** {@inheritDoc} */
99    @Override
100    public void printStackTrace(PrintWriter out) {
101        super.printStackTrace(out);
102        out.println(context);
103    }
104
105    /**
106     * Adds a line of context to this instance.
107     *
108     * @param str {@code non-null;} new context
109     */
110    public void addContext(String str) {
111        if (str == null) {
112            throw new NullPointerException("str == null");
113        }
114
115        context.append(str);
116        if (!str.endsWith("\n")) {
117            context.append('\n');
118        }
119    }
120
121    /**
122     * Gets the context.
123     *
124     * @return {@code non-null;} the context
125     */
126    public String getContext() {
127        return context.toString();
128    }
129
130    /**
131     * Prints the message and context.
132     *
133     * @param out {@code non-null;} where to print to
134     */
135    public void printContext(PrintStream out) {
136        out.println(getMessage());
137        out.print(context);
138    }
139
140    /**
141     * Prints the message and context.
142     *
143     * @param out {@code non-null;} where to print to
144     */
145    public void printContext(PrintWriter out) {
146        out.println(getMessage());
147        out.print(context);
148    }
149}
150