Package com.puppycrawl.tools.checkstyle.checks.blocks

Class EmptyCatchBlockCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable
    public class EmptyCatchBlockCheck
extends AbstractCheck

    Checks for empty catch blocks. There are two options to make validation more precise:

    exceptionVariableName - the name of variable associated with exception, if Check meets variable name matching specified value - empty block is suppressed.
    default value: "^$"

    commentFormat - the format of the first comment inside empty catch block, if Check meets comment inside empty catch block matching specified format - empty block is suppressed. If it is multi-line comment - only its first line is analyzed.
    default value: ".*"
    So, by default Check allows empty catch block with any comment inside.

    If both options are specified - they are applied by any of them is matching.

    Examples:

    To configure the Check to suppress empty catch block if exception's variable name is expected or ignore: 

     <module name="EmptyCatchBlock">
    <property name="exceptionVariableName" value="ignore|expected;/>
 </module>

    Such empty blocks would be both suppressed:

     
 try {
     throw new RuntimeException();
 } catch (RuntimeException expected) {
 }
 
 
 try {
     throw new RuntimeException();
 } catch (RuntimeException ignore) {
 }

    To configure the Check to suppress empty catch block if single-line comment inside is "//This is expected": 

     <module name="EmptyCatchBlock">
    <property name="commentFormat" value="This is expected"/>
 </module>

    Such empty block would be suppressed:

     
 try {
     throw new RuntimeException();
 } catch (RuntimeException ex) {
     //This is expected
 }

    To configure the Check to suppress empty catch block if single-line comment inside is "//This is expected" or exception's variable name is "myException": 

     <module name="EmptyCatchBlock">
    <property name="commentFormat" value="This is expected"/>
    <property name="exceptionVariableName" value="myException"/>
 </module>

    Such empty blocks would be both suppressed:

     
 try {
     throw new RuntimeException();
 } catch (RuntimeException ex) {
     //This is expected
 }
 
 
 try {
     throw new RuntimeException();
 } catch (RuntimeException myException) {

 }

    • Field Detail

      • MSG_KEY_CATCH_BLOCK_EMPTY

        public static final java.lang.String MSG_KEY_CATCH_BLOCK_EMPTY
        A key is pointing to the warning message text in "messages.properties" file.
        See Also:
        Constant Field Values

      • exceptionVariableName

        private java.lang.String exceptionVariableName
        Format of skipping exception's variable name.

      • commentFormat

        private java.lang.String commentFormat
        Format of comment.

      • variableNameRegexp

        private java.util.regex.Pattern variableNameRegexp
        Regular expression pattern compiled from exception's variable name.

      • commentRegexp

        private java.util.regex.Pattern commentRegexp
        Regular expression pattern compiled from comment's format.

    • Constructor Detail

      • EmptyCatchBlockCheck

        public EmptyCatchBlockCheck()

    • Method Detail

      • setExceptionVariableName

        public void setExceptionVariableName​(java.lang.String exceptionVariableName)
        Setter for exception's variable name format.
        Parameters:
        exceptionVariableName - format of exception's variable name.
        Throws:
        org.apache.commons.beanutils.ConversionException - if unable to create Pattern object.

      • setCommentFormat

        public void setCommentFormat​(java.lang.String commentFormat)
        Setter for comment format.
        Parameters:
        commentFormat - format of comment.
        Throws:
        org.apache.commons.beanutils.ConversionException - if unable to create Pattern object.

      • getDefaultTokens

        public int[] getDefaultTokens()
        Description copied from class: AbstractCheck
        Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.
        Specified by:
        getDefaultTokens in class AbstractCheck
        Returns:
        the default tokens
        See Also:
        TokenTypes

      • getAcceptableTokens

        public int[] getAcceptableTokens()
        Description copied from class: AbstractCheck
        The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.
        Specified by:
        getAcceptableTokens in class AbstractCheck
        Returns:
        the token set this check is designed for.
        See Also:
        TokenTypes

      • getRequiredTokens

        public int[] getRequiredTokens()
        Description copied from class: AbstractCheck
        The tokens that this check must be registered for.
        Specified by:
        getRequiredTokens in class AbstractCheck
        Returns:
        the token set this must be registered for.
        See Also:
        TokenTypes

      • isCommentNodesRequired

        public boolean isCommentNodesRequired()
        Description copied from class: AbstractCheck
        Whether comment nodes are required or not.
        Overrides:
        isCommentNodesRequired in class AbstractCheck
        Returns:
        false as a default value.

      • visitCatchBlock

        private void visitCatchBlock​(DetailAST catchAst)
        Visits catch ast node, if it is empty catch block - checks it according to Check's options. If exception's variable name or comment inside block are matching specified regexp - skips from consideration, else - puts violation.
        Parameters:
        catchAst - LITERAL_CATCH

      • getCommentFirstLine

        private static java.lang.String getCommentFirstLine​(DetailAST catchAst)
        Gets the first line of comment in catch block. If comment is single-line - returns it fully, else if comment is multi-line - returns the first line.
        Parameters:
        catchAst - LITERAL_CATCH
        Returns:
        the first line of comment in catch block, "" if no comment was found.

      • isVerifiable

        private boolean isVerifiable​(DetailAST emptyCatchAst,
                             java.lang.String commentContent)
        Checks if current empty catch block is verifiable according to Check's options (exception's variable name and comment format are both in consideration).
        Parameters:
        emptyCatchAst - empty catch LITERAL_CATCH block.
        commentContent - text of comment.
        Returns:
        true if empty catch block is verifiable by Check.

      • isEmptyCatchBlock

        private static boolean isEmptyCatchBlock​(DetailAST catchAst)
        Checks if catch block is empty or contains only comments.
        Parameters:
        catchAst - LITERAL_CATCH
        Returns:
        true if catch block is empty.

      • getExceptionVariableName

        private static java.lang.String getExceptionVariableName​(DetailAST catchAst)
        Gets variable's name associated with exception.
        Parameters:
        catchAst - LITERAL_CATCH
        Returns:
        Variable's name associated with exception.