View Javadoc
1   /**
2    * Logback: the reliable, generic, fast and flexible logging framework.
3    * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
4    *
5    * This program and the accompanying materials are dual-licensed under
6    * either the terms of the Eclipse Public License v1.0 as published by
7    * the Eclipse Foundation
8    *
9    *   or (per the licensee's choosing)
10   *
11   * under the terms of the GNU Lesser General Public License version 2.1
12   * as published by the Free Software Foundation.
13   */
14  package ch.qos.logback.classic.pattern;
15  
16  import ch.qos.logback.classic.ClassicConstants;
17  import ch.qos.logback.core.CoreConstants;
18  
19  public class TargetLengthBasedClassNameAbbreviator implements Abbreviator {
20  
21      final int targetLength;
22  
23      public TargetLengthBasedClassNameAbbreviator(int targetLength) {
24          this.targetLength = targetLength;
25      }
26  
27      public String abbreviate(String fqClassName) {
28          StringBuilder buf = new StringBuilder(targetLength);
29          if (fqClassName == null) {
30              throw new IllegalArgumentException("Class name may not be null");
31          }
32  
33          int inLen = fqClassName.length();
34          if (inLen < targetLength) {
35              return fqClassName;
36          }
37  
38          int[] dotIndexesArray = new int[ClassicConstants.MAX_DOTS];
39          // a.b.c contains 2 dots but 2+1 parts.
40          // see also http://jira.qos.ch/browse/LBCLASSIC-110
41          int[] lengthArray = new int[ClassicConstants.MAX_DOTS + 1];
42  
43          int dotCount = computeDotIndexes(fqClassName, dotIndexesArray);
44  
45          // System.out.println();
46          // System.out.println("Dot count for [" + className + "] is " + dotCount);
47          // if there are not dots than abbreviation is not possible
48          if (dotCount == 0) {
49              return fqClassName;
50          }
51          // printArray("dotArray: ", dotArray);
52          computeLengthArray(fqClassName, dotIndexesArray, lengthArray, dotCount);
53          // printArray("lengthArray: ", lengthArray);
54          for (int i = 0; i <= dotCount; i++) {
55              if (i == 0) {
56                  buf.append(fqClassName.substring(0, lengthArray[i] - 1));
57              } else {
58                  buf.append(fqClassName.substring(dotIndexesArray[i - 1], dotIndexesArray[i - 1] + lengthArray[i]));
59              }
60              // System.out.println("i=" + i + ", buf=" + buf);
61          }
62  
63          return buf.toString();
64      }
65  
66      static int computeDotIndexes(final String className, int[] dotArray) {
67          int dotCount = 0;
68          int k = 0;
69          while (true) {
70              // ignore the $ separator in our computations. This is both convenient
71              // and sensible.
72              k = className.indexOf(CoreConstants.DOT, k);
73              if (k != -1 && dotCount < ClassicConstants.MAX_DOTS) {
74                  dotArray[dotCount] = k;
75                  dotCount++;
76                  k++;
77              } else {
78                  break;
79              }
80          }
81          return dotCount;
82      }
83  
84      void computeLengthArray(final String className, int[] dotArray, int[] lengthArray, int dotCount) {
85          int toTrim = className.length() - targetLength;
86          // System.out.println("toTrim=" + toTrim);
87  
88          // int toTrimAvarage = 0;
89  
90          int len;
91          for (int i = 0; i < dotCount; i++) {
92              int previousDotPosition = -1;
93              if (i > 0) {
94                  previousDotPosition = dotArray[i - 1];
95              }
96              int available = dotArray[i] - previousDotPosition - 1;
97              // System.out.println("i=" + i + ", available = " + available);
98  
99              len = (available < 1) ? available : 1;
100             // System.out.println("i=" + i + ", toTrim = " + toTrim);
101 
102             if (toTrim > 0) {
103                 len = (available < 1) ? available : 1;
104             } else {
105                 len = available;
106             }
107             toTrim -= (available - len);
108             lengthArray[i] = len + 1;
109         }
110 
111         int lastDotIndex = dotCount - 1;
112         lengthArray[dotCount] = className.length() - dotArray[lastDotIndex];
113     }
114 
115     static void printArray(String msg, int[] ia) {
116         System.out.print(msg);
117         for (int i = 0; i < ia.length; i++) {
118             if (i == 0) {
119                 System.out.print(ia[i]);
120             } else {
121                 System.out.print(", " + ia[i]);
122             }
123         }
124         System.out.println();
125     }
126 }