Support multiple bug exclusion files.

Spotbugs always supported multiple files as a comma-separated list in the <excludeFilterFile> configuration option.

This change also adds support for multiple files as a list:

<excludeFilterFiles>
  <excludeFilterFile>...</excludeFilterFile>
  <excludeFilterFile>...</excludeFilterFile>
<excludeFilterFiles>

This allows using pom inheritance to control multiple files.

Includes integration test to verify function.

src/it/exclude-multi-list/invoker.properties

@@ -0,0 +1,4 @@
+invoker.goals = clean compile site
+
+# The expected result of the build, possible values are "success" (default) and "failure"
+invoker.buildResult = success

src/it/exclude-multi-list/pom.xml

@@ -0,0 +1,61 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+    Copyright (C) 2006-2020 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
+
+        https://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.
+-->
+
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>spotbugs-maven-plugin.it</groupId>
+    <artifactId>common</artifactId>
+    <version>testing</version>
+    <relativePath>../common.xml</relativePath>
+  </parent>
+  <artifactId>excludeFile-multi-list</artifactId>
+  <name>excludeFile-multi-list</name>
+  <packaging>jar</packaging>
+  <build>
+    <extensions>
+      <extension>
+        <groupId>spotbugs-maven-plugin.it</groupId>
+        <artifactId>build-tools</artifactId>
+        <version>testing</version>
+      </extension>
+    </extensions>
+  </build>
+  <reporting>
+    <excludeDefaults>true</excludeDefaults>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-jxr-plugin</artifactId>
+        <version>@jxrPluginVersion@</version>
+      </plugin>
+      <plugin>
+        <groupId>com.github.spotbugs</groupId>
+        <artifactId>spotbugs-maven-plugin</artifactId>
+        <configuration>
+          <spotbugsXmlOutput>true</spotbugsXmlOutput>
+          <xmlOutput>true</xmlOutput>
+          <excludeFilterFiles>
+              <excludeFilterFile>whizbang/lib-filter.xml</excludeFilterFile>
+              <excludeFilterFile>filters/lib-filter2.xml</excludeFilterFile>
+          </excludeFilterFiles>
+        </configuration>
+      </plugin>
+    </plugins>
+  </reporting>
+</project>

src/it/exclude-multi-list/verify.groovy

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2006-2020 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
+ *
+ *     https://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 groovy.xml.XmlSlurper
+
+File spotbugsHtml =  new File(basedir, 'target/site/spotbugs.html')
+assert spotbugsHtml.exists()
+
+File spotbugXdoc = new File(basedir, 'target/spotbugs.xml')
+assert spotbugXdoc.exists()
+
+File spotbugXml = new File(basedir, 'target/spotbugsXml.xml')
+assert spotbugXml.exists()
+
+
+println '***************************'
+println "Checking HTML file"
+println '***************************'
+
+def xhtmlParser = new XmlSlurper();
+xhtmlParser.setFeature("http://apache.org/xml/features/disallow-doctype-decl", false)
+xhtmlParser.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false)
+def path = xhtmlParser.parse( spotbugsHtml )
+//*[@id="contentBox"]/div[2]/table/tbody/tr[2]/td[2]
+def spotbugsErrors = path.body.'**'.find {div -> div.@id == 'contentBox'}.section[1].table.tr[1].td[1].toInteger()
+println "Error Count is ${spotbugsErrors}"
+
+
+println '**********************************'
+println "Checking Spotbugs Native XML file"
+println '**********************************'
+
+path = new XmlSlurper().parse(spotbugXml)
+
+allNodes = path.depthFirst().collect{ it }
+def spotbugsXmlErrors = allNodes.findAll {it.name() == 'BugInstance'}.size()
+println "BugInstance size is ${spotbugsXmlErrors}"
+
+
+println '***************************'
+println "Checking xDoc file"
+println '***************************'
+
+path = new XmlSlurper().parse(spotbugXdoc)
+
+allNodes = path.depthFirst().collect{ it }
+def xdocErrors = allNodes.findAll {it.name() == 'BugInstance'}.size()
+println "BugInstance size is ${xdocErrors}"
+
+
+assert xdocErrors == spotbugsXmlErrors
+
+assert spotbugsErrors == spotbugsXmlErrors

src/main/groovy/org/codehaus/mojo/spotbugs/SpotBugsMojo.groovy

@@ -330,6 +330,28 @@ class SpotBugsMojo extends AbstractMavenReport implements SpotBugsPluginsTrait {
     @Parameter(property = "spotbugs.excludeFilterFile")
     String excludeFilterFile
 
+    /**
+     * <p>
+     * File name for exclude filter files. Bugs matching the filters are not reported.
+     * </p>
+     *
+     * <p>
+     * This is an alternative to <code>&lt;excludeFilterFile&gt;</code> which allows multiple
+     * files to be specified as separate elements in a pom.
+     * </p>
+     *
+     * <p>
+     * This parameter is resolved as resource, URL, then file. If successfully
+     * resolved, the contents of the configuration is copied into the
+     * <code>${project.build.directory}</code>
+     * directory before being passed to Spotbugs as a filter file.
+     * </p>
+     *
+     * @since 4.7.0.1-SNAPSHOT
+     */
+    @Parameter(property = "spotbugs.excludeFilterFiles")
+    List excludeFilterFiles
+
     /**
      * <p>
      * File names of the baseline files. Bugs found in the baseline files won't be reported.
@@ -961,6 +983,16 @@ class SpotBugsMojo extends AbstractMavenReport implements SpotBugsPluginsTrait {
 
         }
 
+        if (excludeFilterFiles) {
+            log.debug("  Adding Exclude Filter Files ")
+
+            excludeFilterFiles.each { excludeFilter ->
+                args << "-exclude"
+                args << resourceHelper.getResourceFile(excludeFilter.trim())
+            }
+
+        }
+
         if (excludeBugsFile) {
             log.debug("  Adding Exclude Bug Files (Baselines)")
             String[] excludeFiles = excludeBugsFile.split(SpotBugsInfo.COMMA)