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Checkstyle is a development tool to help programmers write Java code
that adheres to a coding standard
////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2016 the original author or authors.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
////////////////////////////////////////////////////////////////////////////////
package com.puppycrawl.tools.checkstyle.checks.design;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
/**
*
* Restricts throws statements to a specified count (default = 4).
* Methods with "Override" or "java.lang.Override" annotation are skipped
* from validation as current class cannot change signature of these methods.
*
*
* Rationale:
* Exceptions form part of a methods interface. Declaring
* a method to throw too many differently rooted
* exceptions makes exception handling onerous and leads
* to poor programming practices such as catch
* (Exception). 4 is the empirical value which is based
* on reports that we had for the ThrowsCountCheck over big projects
* such as OpenJDK. This check also forces developers to put exceptions
* into a hierarchy such that in the simplest
* case, only one type of exception need be checked for by
* a caller but allows any sub-classes to be caught
* specifically if necessary. For more information on rules
* for the exceptions and their issues, see Effective Java:
* Programming Language Guide Second Edition
* by Joshua Bloch pages 264-273.
*
*
* ignorePrivateMethods - allows to skip private methods as they do
* not cause problems for other classes.
*
* @author Simon Harris
*/
public final class ThrowsCountCheck extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY = "throws.count";
/** Default value of max property. */
private static final int DEFAULT_MAX = 4;
/** Whether private methods must be ignored. **/
private boolean ignorePrivateMethods = true;
/** Maximum allowed throws statements. */
private int max;
/** Creates new instance of the check. */
public ThrowsCountCheck() {
max = DEFAULT_MAX;
}
@Override
public int[] getDefaultTokens() {
return new int[] {
TokenTypes.LITERAL_THROWS,
};
}
@Override
public int[] getRequiredTokens() {
return getDefaultTokens();
}
@Override
public int[] getAcceptableTokens() {
return new int[] {
TokenTypes.LITERAL_THROWS,
};
}
/**
* Sets whether private methods must be ignored.
* @param ignorePrivateMethods whether private methods must be ignored.
*/
public void setIgnorePrivateMethods(boolean ignorePrivateMethods) {
this.ignorePrivateMethods = ignorePrivateMethods;
}
/**
* Setter for max property.
* @param max maximum allowed throws statements.
*/
public void setMax(int max) {
this.max = max;
}
@Override
public void visitToken(DetailAST ast) {
if (ast.getType() == TokenTypes.LITERAL_THROWS) {
visitLiteralThrows(ast);
}
else {
throw new IllegalStateException(ast.toString());
}
}
/**
* Checks number of throws statements.
* @param ast throws for check.
*/
private void visitLiteralThrows(DetailAST ast) {
if ((!ignorePrivateMethods || !isInPrivateMethod(ast))
&& !isOverriding(ast)) {
// Account for all the commas!
final int count = (ast.getChildCount() + 1) / 2;
if (count > max) {
log(ast.getLineNo(), ast.getColumnNo(), MSG_KEY,
count, max);
}
}
}
/**
* Check if a method has annotation @Override.
* @param ast throws, which is being checked.
* @return true, if a method has annotation @Override.
*/
private static boolean isOverriding(DetailAST ast) {
final DetailAST modifiers = ast.getParent().findFirstToken(TokenTypes.MODIFIERS);
boolean isOverriding = false;
if (modifiers.branchContains(TokenTypes.ANNOTATION)) {
DetailAST child = modifiers.getFirstChild();
while (child != null) {
if (child.getType() == TokenTypes.ANNOTATION
&& "Override".equals(getAnnotationName(child))) {
isOverriding = true;
}
child = child.getNextSibling();
}
}
return isOverriding;
}
/**
* Gets name of an annotation.
* @param annotation to get name of.
* @return name of an annotation.
*/
private static String getAnnotationName(DetailAST annotation) {
final DetailAST dotAst = annotation.findFirstToken(TokenTypes.DOT);
final String name;
if (dotAst == null) {
name = annotation.findFirstToken(TokenTypes.IDENT).getText();
}
else {
name = dotAst.findFirstToken(TokenTypes.IDENT).getText();
}
return name;
}
/**
* Checks if method, which throws an exception is private.
* @param ast throws, which is being checked.
* @return true, if method, which throws an exception is private.
*/
private static boolean isInPrivateMethod(DetailAST ast) {
final DetailAST methodModifiers = ast.getParent().findFirstToken(TokenTypes.MODIFIERS);
return methodModifiers.findFirstToken(TokenTypes.LITERAL_PRIVATE) != null;
}
}