1 /*
2  * Copyright (C) 2006 Google Inc.
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 
17 package com.google.inject.internal.util;
18 
19 import com.google.common.base.Preconditions;
20 import com.google.common.collect.ImmutableSet;
21 import com.google.common.collect.Lists;
22 import java.util.List;
23 
24 /**
25  * Provides access to the calling line of code.
26  *
27  * @author crazybob@google.com (Bob Lee)
28  */
29 public final class SourceProvider {
30 
31   /** Indicates that the source is unknown. */
32   public static final Object UNKNOWN_SOURCE = "[unknown source]";
33 
34   private final SourceProvider parent;
35   private final ImmutableSet<String> classNamesToSkip;
36 
37   public static final SourceProvider DEFAULT_INSTANCE =
38       new SourceProvider(ImmutableSet.of(SourceProvider.class.getName()));
39 
SourceProvider(Iterable<String> classesToSkip)40   private SourceProvider(Iterable<String> classesToSkip) {
41     this(null, classesToSkip);
42   }
43 
SourceProvider(SourceProvider parent, Iterable<String> classesToSkip)44   private SourceProvider(SourceProvider parent, Iterable<String> classesToSkip) {
45     this.parent = parent;
46 
47     ImmutableSet.Builder<String> classNamesToSkipBuilder = ImmutableSet.builder();
48     for (String classToSkip : classesToSkip) {
49       if (parent == null || !parent.shouldBeSkipped(classToSkip)) {
50         classNamesToSkipBuilder.add(classToSkip);
51       }
52     }
53     this.classNamesToSkip = classNamesToSkipBuilder.build();
54   }
55 
56   /** Returns a new instance that also skips {@code moreClassesToSkip}. */
plusSkippedClasses(Class... moreClassesToSkip)57   public SourceProvider plusSkippedClasses(Class... moreClassesToSkip) {
58     return new SourceProvider(this, asStrings(moreClassesToSkip));
59   }
60 
61   /** Returns true if the className should be skipped. */
shouldBeSkipped(String className)62   private boolean shouldBeSkipped(String className) {
63     return (parent != null && parent.shouldBeSkipped(className))
64         || classNamesToSkip.contains(className);
65   }
66 
67   /** Returns the class names as Strings */
asStrings(Class... classes)68   private static List<String> asStrings(Class... classes) {
69     List<String> strings = Lists.newArrayList();
70     for (Class c : classes) {
71       strings.add(c.getName());
72     }
73     return strings;
74   }
75 
76   /**
77    * Returns the calling line of code. The selected line is the nearest to the top of the stack that
78    * is not skipped.
79    */
get(StackTraceElement[] stackTraceElements)80   public StackTraceElement get(StackTraceElement[] stackTraceElements) {
81     Preconditions.checkNotNull(stackTraceElements, "The stack trace elements cannot be null.");
82     for (final StackTraceElement element : stackTraceElements) {
83       String className = element.getClassName();
84 
85       if (!shouldBeSkipped(className)) {
86         return element;
87       }
88     }
89     throw new AssertionError();
90   }
91 
92   /** Returns the non-skipped module class name. */
getFromClassNames(List<String> moduleClassNames)93   public Object getFromClassNames(List<String> moduleClassNames) {
94     Preconditions.checkNotNull(moduleClassNames, "The list of module class names cannot be null.");
95     for (final String moduleClassName : moduleClassNames) {
96       if (!shouldBeSkipped(moduleClassName)) {
97         return new StackTraceElement(moduleClassName, "configure", null, -1);
98       }
99     }
100     return UNKNOWN_SOURCE;
101   }
102 }
103