Replace import-control checkstyle file with regex

Fix Eclipse build warnings by replacing checkstyle's import-control file
with a simple regex rule.

Fixes gh-4006

spring-boot-parent/pom.xml

@@ -444,30 +444,6 @@
 			</plugins>
 		</pluginManagement>
 		<plugins>
-			<plugin>
-				<groupId>org.apache.maven.plugins</groupId>
-				<artifactId>maven-resources-plugin</artifactId>
-				<executions>
-					<execution>
-						<id>checkstyle-prepare</id>
-						<phase>validate</phase>
-						<goals>
-							<goal>copy-resources</goal>
-						</goals>
-						<configuration>
-							<outputDirectory>${project.build.directory}</outputDirectory>
-							<resources>
-								<resource>
-									<directory>${main.basedir}/spring-boot-parent/src/checkstyle</directory>
-									<includes>
-										<include>checkstyle-import-control.xml</include>
-									</includes>
-								</resource>
-							</resources>
-						</configuration>
-					</execution>
-				</executions>
-			</plugin>
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-checkstyle-plugin</artifactId>

spring-boot-parent/src/checkstyle/checkstyle-import-control.xml

@@ -1,12 +0,0 @@
-<?xml version="1.0"?>
-<!DOCTYPE import-control PUBLIC "-//Puppy Crawl//DTD Import Control 1.1//EN" "http://www.puppycrawl.com/dtds/import_control_1_1.dtd">
-<import-control pkg="org.springframework.boot">
-
-	<allow pkg=".*" regex="true"/>
-
-	<!-- Use BDD Mockito -->
-	<disallow class="org.mockito.Mockito.when"/>
-	<disallow class="org.mockito.Mockito.doThrow"/>
-	<disallow class="org.mockito.Mockito.doAnswer"/>
-
-</import-control>

spring-boot-parent/src/checkstyle/checkstyle.xml

@@ -83,9 +83,6 @@
 			<property name="option" value="bottom" />
 			<property name="sortStaticImportsAlphabetically" value="true" />
 		</module>
-		<module name="ImportControl">
-			<property name="file" value="${checkstyle.build.directory}/checkstyle-import-control.xml"/>
-		</module>
 
 		<!-- Javadoc Comments -->
 		<module name="JavadocType">
@@ -130,6 +127,13 @@
 				value="Line has leading space characters; indentation should be performed with tabs only." />
 			<property name="ignoreComments" value="true" />
 		</module>
+ 		<module name="RegexpSinglelineJava">
+ 			<property name="maximum" value="0"/>
+			<property name="format" value="org\.mockito\.Mockito\.(when|doThrow|doAnswer)" />
+			<property name="message"
+				value="Please use BDDMockto imports." />
+			<property name="ignoreComments" value="true" />
+		</module>
 		<module name="Regexp">
 			<property name="format" value="[ \t]+$" />
 			<property name="illegalPattern" value="true" />