Coverage Report - com.puppycrawl.tools.checkstyle.checks.blocks.EmptyCatchBlockCheck
 
Classes in this File Line Coverage Branch Coverage Complexity
EmptyCatchBlockCheck
100%
54/54
100%
26/26
1.917
 
 1  
 ////////////////////////////////////////////////////////////////////////////////
 2  
 // checkstyle: Checks Java source code for adherence to a set of rules.
 3  
 // Copyright (C) 2001-2017 the original author or authors.
 4  
 //
 5  
 // This library is free software; you can redistribute it and/or
 6  
 // modify it under the terms of the GNU Lesser General Public
 7  
 // License as published by the Free Software Foundation; either
 8  
 // version 2.1 of the License, or (at your option) any later version.
 9  
 //
 10  
 // This library is distributed in the hope that it will be useful,
 11  
 // but WITHOUT ANY WARRANTY; without even the implied warranty of
 12  
 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 13  
 // Lesser General Public License for more details.
 14  
 //
 15  
 // You should have received a copy of the GNU Lesser General Public
 16  
 // License along with this library; if not, write to the Free Software
 17  
 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 18  
 ////////////////////////////////////////////////////////////////////////////////
 19  
 
 20  
 package com.puppycrawl.tools.checkstyle.checks.blocks;
 21  
 
 22  
 import java.util.regex.Pattern;
 23  
 
 24  
 import com.puppycrawl.tools.checkstyle.StatelessCheck;
 25  
 import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
 26  
 import com.puppycrawl.tools.checkstyle.api.DetailAST;
 27  
 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
 28  
 import com.puppycrawl.tools.checkstyle.utils.CommonUtils;
 29  
 
 30  
 /**
 31  
  * <p>
 32  
  * Checks for empty catch blocks. There are two options to make validation more precise:
 33  
  * </p>
 34  
  *
 35  
  * <p><b>exceptionVariableName</b> - the name of variable associated with exception,
 36  
  * if Check meets variable name matching specified value - empty block is suppressed.<br>
 37  
  *  default value: &quot;^$&quot;
 38  
  * </p>
 39  
  *
 40  
  * <p><b>commentFormat</b> - the format of the first comment inside empty catch
 41  
  * block, if Check meets comment inside empty catch block matching specified format
 42  
  *  - empty block is suppressed. If it is multi-line comment - only its first line is analyzed.<br>
 43  
  * default value: &quot;.*&quot;<br>
 44  
  * So, by default Check allows empty catch block with any comment inside.
 45  
  * </p>
 46  
  * <p>
 47  
  * If both options are specified - they are applied by <b>any of them is matching</b>.
 48  
  * </p>
 49  
  * Examples:
 50  
  * <p>
 51  
  * To configure the Check to suppress empty catch block if exception's variable name is
 52  
  *  <b>expected</b> or <b>ignore</b>:
 53  
  * </p>
 54  
  * <pre>
 55  
  * &lt;module name=&quot;EmptyCatchBlock&quot;&gt;
 56  
  *    &lt;property name=&quot;exceptionVariableName&quot; value=&quot;ignore|expected;/&gt;
 57  
  * &lt;/module&gt;
 58  
  * </pre>
 59  
  *
 60  
  * <p>Such empty blocks would be both suppressed:<br>
 61  
  * </p>
 62  
  * <pre>
 63  
  * {@code
 64  
  * try {
 65  
  *     throw new RuntimeException();
 66  
  * } catch (RuntimeException expected) {
 67  
  * }
 68  
  * }
 69  
  * {@code
 70  
  * try {
 71  
  *     throw new RuntimeException();
 72  
  * } catch (RuntimeException ignore) {
 73  
  * }
 74  
  * }
 75  
  * </pre>
 76  
  * <p>
 77  
  * To configure the Check to suppress empty catch block if single-line comment inside
 78  
  *  is &quot;//This is expected&quot;:
 79  
  * </p>
 80  
  * <pre>
 81  
  * &lt;module name=&quot;EmptyCatchBlock&quot;&gt;
 82  
  *    &lt;property name=&quot;commentFormat&quot; value=&quot;This is expected&quot;/&gt;
 83  
  * &lt;/module&gt;
 84  
  * </pre>
 85  
  *
 86  
  * <p>Such empty block would be suppressed:<br>
 87  
  * </p>
 88  
  * <pre>
 89  
  * {@code
 90  
  * try {
 91  
  *     throw new RuntimeException();
 92  
  * } catch (RuntimeException ex) {
 93  
  *     //This is expected
 94  
  * }
 95  
  * }
 96  
  * </pre>
 97  
  * <p>
 98  
  * To configure the Check to suppress empty catch block if single-line comment inside
 99  
  *  is &quot;//This is expected&quot; or exception's variable name is &quot;myException&quot;:
 100  
  * </p>
 101  
  * <pre>
 102  
  * &lt;module name=&quot;EmptyCatchBlock&quot;&gt;
 103  
  *    &lt;property name=&quot;commentFormat&quot; value=&quot;This is expected&quot;/&gt;
 104  
  *    &lt;property name=&quot;exceptionVariableName&quot; value=&quot;myException&quot;/&gt;
 105  
  * &lt;/module&gt;
 106  
  * </pre>
 107  
  *
 108  
  * <p>Such empty blocks would be both suppressed:<br>
 109  
  * </p>
 110  
  * <pre>
 111  
  * {@code
 112  
  * try {
 113  
  *     throw new RuntimeException();
 114  
  * } catch (RuntimeException ex) {
 115  
  *     //This is expected
 116  
  * }
 117  
  * }
 118  
  * {@code
 119  
  * try {
 120  
  *     throw new RuntimeException();
 121  
  * } catch (RuntimeException myException) {
 122  
  *
 123  
  * }
 124  
  * }
 125  
  * </pre>
 126  
  * @author <a href="mailto:nesterenko-aleksey@list.ru">Aleksey Nesterenko</a>
 127  
  */
 128  
 @StatelessCheck
 129  15
 public class EmptyCatchBlockCheck extends AbstractCheck {
 130  
 
 131  
     /**
 132  
      * A key is pointing to the warning message text in "messages.properties"
 133  
      * file.
 134  
      */
 135  
     public static final String MSG_KEY_CATCH_BLOCK_EMPTY = "catch.block.empty";
 136  
 
 137  
     /** Format of skipping exception's variable name. */
 138  15
     private String exceptionVariableName = "^$";
 139  
 
 140  
     /** Format of comment. */
 141  15
     private String commentFormat = ".*";
 142  
 
 143  
     /**
 144  
      * Regular expression pattern compiled from exception's variable name.
 145  
      */
 146  15
     private Pattern variableNameRegexp = Pattern.compile(exceptionVariableName);
 147  
 
 148  
     /**
 149  
      * Regular expression pattern compiled from comment's format.
 150  
      */
 151  15
     private Pattern commentRegexp = Pattern.compile(commentFormat);
 152  
 
 153  
     /**
 154  
      * Setter for exception's variable name format.
 155  
      * @param exceptionVariableName
 156  
      *        format of exception's variable name.
 157  
      * @throws org.apache.commons.beanutils.ConversionException
 158  
      *         if unable to create Pattern object.
 159  
      */
 160  
     public void setExceptionVariableName(String exceptionVariableName) {
 161  4
         this.exceptionVariableName = exceptionVariableName;
 162  4
         variableNameRegexp = CommonUtils.createPattern(exceptionVariableName);
 163  4
     }
 164  
 
 165  
     /**
 166  
      * Setter for comment format.
 167  
      * @param commentFormat
 168  
      *        format of comment.
 169  
      * @throws org.apache.commons.beanutils.ConversionException
 170  
      *         if unable to create Pattern object.
 171  
      */
 172  
     public void setCommentFormat(String commentFormat) {
 173  3
         this.commentFormat = commentFormat;
 174  3
         commentRegexp = CommonUtils.createPattern(commentFormat);
 175  3
     }
 176  
 
 177  
     @Override
 178  
     public int[] getDefaultTokens() {
 179  19
         return getRequiredTokens();
 180  
     }
 181  
 
 182  
     @Override
 183  
     public int[] getAcceptableTokens() {
 184  6
         return getRequiredTokens();
 185  
     }
 186  
 
 187  
     @Override
 188  
     public int[] getRequiredTokens() {
 189  45
         return new int[] {
 190  
             TokenTypes.LITERAL_CATCH,
 191  
         };
 192  
     }
 193  
 
 194  
     @Override
 195  
     public boolean isCommentNodesRequired() {
 196  14
         return true;
 197  
     }
 198  
 
 199  
     @Override
 200  
     public void visitToken(DetailAST ast) {
 201  46
         visitCatchBlock(ast);
 202  46
     }
 203  
 
 204  
     /**
 205  
      * Visits catch ast node, if it is empty catch block - checks it according to
 206  
      *  Check's options. If exception's variable name or comment inside block are matching
 207  
      *   specified regexp - skips from consideration, else - puts violation.
 208  
      * @param catchAst {@link TokenTypes#LITERAL_CATCH LITERAL_CATCH}
 209  
      */
 210  
     private void visitCatchBlock(DetailAST catchAst) {
 211  46
         if (isEmptyCatchBlock(catchAst)) {
 212  28
             final String commentContent = getCommentFirstLine(catchAst);
 213  28
             if (isVerifiable(catchAst, commentContent)) {
 214  10
                 log(catchAst.getLineNo(), MSG_KEY_CATCH_BLOCK_EMPTY);
 215  
             }
 216  
         }
 217  46
     }
 218  
 
 219  
     /**
 220  
      * Gets the first line of comment in catch block. If comment is single-line -
 221  
      *  returns it fully, else if comment is multi-line - returns the first line.
 222  
      * @param catchAst {@link TokenTypes#LITERAL_CATCH LITERAL_CATCH}
 223  
      * @return the first line of comment in catch block, "" if no comment was found.
 224  
      */
 225  
     private static String getCommentFirstLine(DetailAST catchAst) {
 226  28
         final DetailAST slistToken = catchAst.getLastChild();
 227  28
         final DetailAST firstElementInBlock = slistToken.getFirstChild();
 228  28
         String commentContent = "";
 229  28
         if (firstElementInBlock.getType() == TokenTypes.SINGLE_LINE_COMMENT) {
 230  12
             commentContent = firstElementInBlock.getFirstChild().getText();
 231  
         }
 232  16
         else if (firstElementInBlock.getType() == TokenTypes.BLOCK_COMMENT_BEGIN) {
 233  12
             commentContent = firstElementInBlock.getFirstChild().getText();
 234  12
             final String[] lines = commentContent.split(System.getProperty("line.separator"));
 235  14
             for (String line : lines) {
 236  12
                 if (!line.isEmpty()) {
 237  10
                     commentContent = line;
 238  10
                     break;
 239  
                 }
 240  
             }
 241  
         }
 242  28
         return commentContent;
 243  
     }
 244  
 
 245  
     /**
 246  
      * Checks if current empty catch block is verifiable according to Check's options
 247  
      *  (exception's variable name and comment format are both in consideration).
 248  
      * @param emptyCatchAst empty catch {@link TokenTypes#LITERAL_CATCH LITERAL_CATCH} block.
 249  
      * @param commentContent text of comment.
 250  
      * @return true if empty catch block is verifiable by Check.
 251  
      */
 252  
     private boolean isVerifiable(DetailAST emptyCatchAst, String commentContent) {
 253  28
         final String variableName = getExceptionVariableName(emptyCatchAst);
 254  28
         final boolean isMatchingVariableName = variableNameRegexp
 255  28
                 .matcher(variableName).find();
 256  28
         final boolean isMatchingCommentContent = !commentContent.isEmpty()
 257  24
                  && commentRegexp.matcher(commentContent).find();
 258  28
         return !isMatchingVariableName && !isMatchingCommentContent;
 259  
     }
 260  
 
 261  
     /**
 262  
      * Checks if catch block is empty or contains only comments.
 263  
      * @param catchAst {@link TokenTypes#LITERAL_CATCH LITERAL_CATCH}
 264  
      * @return true if catch block is empty.
 265  
      */
 266  
     private static boolean isEmptyCatchBlock(DetailAST catchAst) {
 267  46
         boolean result = true;
 268  46
         final DetailAST slistToken = catchAst.findFirstToken(TokenTypes.SLIST);
 269  46
         DetailAST catchBlockStmt = slistToken.getFirstChild();
 270  82
         while (catchBlockStmt.getType() != TokenTypes.RCURLY) {
 271  54
             if (catchBlockStmt.getType() != TokenTypes.SINGLE_LINE_COMMENT
 272  34
                  && catchBlockStmt.getType() != TokenTypes.BLOCK_COMMENT_BEGIN) {
 273  18
                 result = false;
 274  18
                 break;
 275  
             }
 276  36
             catchBlockStmt = catchBlockStmt.getNextSibling();
 277  
         }
 278  46
         return result;
 279  
     }
 280  
 
 281  
     /**
 282  
      * Gets variable's name associated with exception.
 283  
      * @param catchAst {@link TokenTypes#LITERAL_CATCH LITERAL_CATCH}
 284  
      * @return Variable's name associated with exception.
 285  
      */
 286  
     private static String getExceptionVariableName(DetailAST catchAst) {
 287  28
         final DetailAST parameterDef = catchAst.findFirstToken(TokenTypes.PARAMETER_DEF);
 288  28
         final DetailAST variableName = parameterDef.findFirstToken(TokenTypes.IDENT);
 289  28
         return variableName.getText();
 290  
     }
 291  
 
 292  
 }