Fix checkstyle plugin, fix errors reported by checkstyle

.mvn/wrapper/MavenWrapperDownloader.java

@@ -0,0 +1,117 @@
+/*
+ * Copyright 2007-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import java.net.*;
+import java.io.*;
+import java.nio.channels.*;
+import java.util.Properties;
+
+public class MavenWrapperDownloader {
+
+    private static final String WRAPPER_VERSION = "0.5.6";
+    /**
+     * Default URL to download the maven-wrapper.jar from, if no 'downloadUrl' is provided.
+     */
+    private static final String DEFAULT_DOWNLOAD_URL = "https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/"
+        + WRAPPER_VERSION + "/maven-wrapper-" + WRAPPER_VERSION + ".jar";
+
+    /**
+     * Path to the maven-wrapper.properties file, which might contain a downloadUrl property to
+     * use instead of the default one.
+     */
+    private static final String MAVEN_WRAPPER_PROPERTIES_PATH =
+            ".mvn/wrapper/maven-wrapper.properties";
+
+    /**
+     * Path where the maven-wrapper.jar will be saved to.
+     */
+    private static final String MAVEN_WRAPPER_JAR_PATH =
+            ".mvn/wrapper/maven-wrapper.jar";
+
+    /**
+     * Name of the property which should be used to override the default download url for the wrapper.
+     */
+    private static final String PROPERTY_NAME_WRAPPER_URL = "wrapperUrl";
+
+    public static void main(String args[]) {
+        System.out.println("- Downloader started");
+        File baseDirectory = new File(args[0]);
+        System.out.println("- Using base directory: " + baseDirectory.getAbsolutePath());
+
+        // If the maven-wrapper.properties exists, read it and check if it contains a custom
+        // wrapperUrl parameter.
+        File mavenWrapperPropertyFile = new File(baseDirectory, MAVEN_WRAPPER_PROPERTIES_PATH);
+        String url = DEFAULT_DOWNLOAD_URL;
+        if(mavenWrapperPropertyFile.exists()) {
+            FileInputStream mavenWrapperPropertyFileInputStream = null;
+            try {
+                mavenWrapperPropertyFileInputStream = new FileInputStream(mavenWrapperPropertyFile);
+                Properties mavenWrapperProperties = new Properties();
+                mavenWrapperProperties.load(mavenWrapperPropertyFileInputStream);
+                url = mavenWrapperProperties.getProperty(PROPERTY_NAME_WRAPPER_URL, url);
+            } catch (IOException e) {
+                System.out.println("- ERROR loading '" + MAVEN_WRAPPER_PROPERTIES_PATH + "'");
+            } finally {
+                try {
+                    if(mavenWrapperPropertyFileInputStream != null) {
+                        mavenWrapperPropertyFileInputStream.close();
+                    }
+                } catch (IOException e) {
+                    // Ignore ...
+                }
+            }
+        }
+        System.out.println("- Downloading from: " + url);
+
+        File outputFile = new File(baseDirectory.getAbsolutePath(), MAVEN_WRAPPER_JAR_PATH);
+        if(!outputFile.getParentFile().exists()) {
+            if(!outputFile.getParentFile().mkdirs()) {
+                System.out.println(
+                        "- ERROR creating output directory '" + outputFile.getParentFile().getAbsolutePath() + "'");
+            }
+        }
+        System.out.println("- Downloading to: " + outputFile.getAbsolutePath());
+        try {
+            downloadFileFromURL(url, outputFile);
+            System.out.println("Done");
+            System.exit(0);
+        } catch (Throwable e) {
+            System.out.println("- Error downloading");
+            e.printStackTrace();
+            System.exit(1);
+        }
+    }
+
+    private static void downloadFileFromURL(String urlString, File destination) throws Exception {
+        if (System.getenv("MVNW_USERNAME") != null && System.getenv("MVNW_PASSWORD") != null) {
+            String username = System.getenv("MVNW_USERNAME");
+            char[] password = System.getenv("MVNW_PASSWORD").toCharArray();
+            Authenticator.setDefault(new Authenticator() {
+                @Override
+                protected PasswordAuthentication getPasswordAuthentication() {
+                    return new PasswordAuthentication(username, password);
+                }
+            });
+        }
+        URL website = new URL(urlString);
+        ReadableByteChannel rbc;
+        rbc = Channels.newChannel(website.openStream());
+        FileOutputStream fos = new FileOutputStream(destination);
+        fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
+        fos.close();
+        rbc.close();
+    }
+
+}

.mvn/wrapper/maven-wrapper.properties

@@ -0,0 +1,2 @@
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.6.3/apache-maven-3.6.3-bin.zip
+wrapperUrl=https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar

CONTRIBUTING.md

@@ -26,7 +26,7 @@ be accepted under the terms of that license.
 Checkstyle failures during compilation indicate errors in your style and will
 be displayed in the console output of the build (including in Travis-CI output),
 or can be viewed in the `checkstyle-result.xml` file.  To save yourself some
-hassle, consider executing checkstyle first per: 'mvn checkstyle:checkstyle'.
+hassle, consider executing checkstyle first per: `mvn checkstyle:checkstyle`.
 It's fast, and will catch style errors early.
 
 Before your code can be accepted into the project you must sign the

checkstyle.xml

@@ -1,9 +1,11 @@
 <?xml version="1.0"?>
 <!DOCTYPE module PUBLIC
-    "-//Puppy Crawl//DTD Check Configuration 1.2//EN"
-    "http://www.puppycrawl.com/dtds/configuration_1_2.dtd">
+    "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+    "https://checkstyle.org/dtds/configuration_1_3.dtd">
 
 <module name="Checker">
+        <property name="cacheFile" value="${checkstyle.cache.file}"/>
+
     <!--module name="NewlineAtEndOfFile"/-->
     <module name="FileLength"/>
     <module name="FileTabCharacter"/>
@@ -26,9 +28,13 @@
         <property name="message" value="Space needed around ':' character."/>
     </module>
 
-    <module name="TreeWalker">
-        <property name="cacheFile" value="${checkstyle.cache.file}"/>
+        <!-- Checks for Size Violations.                    -->
+        <!-- See http://checkstyle.sf.net/config_sizes.html#LineLength -->
+        <module name="LineLength">
+            <property name="max" value="100"/>
+        </module>
 
+    <module name="TreeWalker">
         <!-- Checks for Javadoc comments.                     -->
         <!-- See http://checkstyle.sf.net/config_javadoc.html -->
         <!--module name="JavadocMethod"/-->
@@ -61,10 +67,7 @@
 
 
         <!-- Checks for Size Violations.                    -->
-        <!-- See http://checkstyle.sf.net/config_sizes.html -->
-        <module name="LineLength">
-            <property name="max" value="100"/>
-        </module>
+        <!-- See http://checkstyle.sf.net/config_sizes.html#MethodLength -->
         <module name="MethodLength"/>
         <!--module name="ParameterNumber"/-->
 
@@ -105,7 +108,6 @@
         <!-- See http://checkstyle.sf.net/config_coding.html -->
         <!--module name="AvoidInlineConditionals"/-->
         <module name="CovariantEquals"/>
-        <module name="DoubleCheckedLocking"/>
         <module name="EmptyStatement"/>
         <!--<module name="EqualsAvoidNull"/>-->
         <module name="EqualsHashCode"/>
@@ -114,7 +116,6 @@
         <!--<module name="InnerAssignment"/>-->
         <!--module name="MagicNumber"/-->
         <!-- <module name="MissingSwitchDefault"/> -->
-        <module name="RedundantThrows"/>
         <module name="SimplifyBooleanExpression"/>
         <module name="SimplifyBooleanReturn"/>
 
@@ -133,11 +134,11 @@
         <!--module name="FinalParameters"/-->
         <!--module name="TodoComment"/-->
         <module name="UpperEll"/>
-
-        <!-- Enable suppression later -->
-        <module name="FileContentsHolder"/>
+
+
+        <!-- Allow suppression via comments -->
+        <module name="SuppressionCommentFilter"/>
+
     </module>
-
-    <!-- Allow suppression via comments -->
-    <module name="SuppressionCommentFilter"/>
+
 </module>