Add @ConditionalOnMissingFilterBean

Add a new condition that can be used to check for servlet `Filter`
beans that are either registered directly, or via a
`FilterRegistrationBean`.

Closes gh-14940

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/ConditionalOnMissingFilterBean.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2012-2018 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.
+ */
+
+package org.springframework.boot.autoconfigure.web.servlet;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import javax.servlet.Filter;
+
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.web.servlet.FilterRegistrationBean;
+import org.springframework.context.annotation.Conditional;
+import org.springframework.core.annotation.AliasFor;
+
+/**
+ * {@link Conditional} that only matches when no {@link Filter} beans of the specified
+ * type are contained in the {@link BeanFactory}. This condition will detect both directly
+ * register {@link Filter} beans as well as those registered via a
+ * {@link FilterRegistrationBean}.
+ * <p>
+ * When placed on a {@code @Bean} method, the bean class defaults to the return type of
+ * the factory method:
+ *
+ * @author Phillip Webb
+ * @since 2.1.0
+ */
+@Target({ ElementType.TYPE, ElementType.METHOD })
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+@ConditionalOnMissingBean(parameterizedContainer = FilterRegistrationBean.class)
+public @interface ConditionalOnMissingFilterBean {
+
+	/**
+	 * The filter bean type that must not be present.
+	 * @return the bean type
+	 */
+	@AliasFor(annotation = ConditionalOnMissingBean.class)
+	Class<? extends Filter>[] value() default {};
+
+}

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/servlet/ConditionalOnMissingFilterBeanTests.java

@@ -0,0 +1,223 @@
+/*
+ * Copyright 2012-2018 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.
+ */
+
+package org.springframework.boot.autoconfigure.web.servlet;
+
+import java.io.IOException;
+import java.util.function.Consumer;
+
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+
+import org.junit.Test;
+
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.boot.web.servlet.FilterRegistrationBean;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.util.StringUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ConditionalOnMissingFilterBean}.
+ *
+ * @author Phillip Webb
+ */
+public class ConditionalOnMissingFilterBeanTests {
+
+	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner();
+
+	@Test
+	public void outcomeWhenValueIsOfMissingBeanReturnsMatch() {
+
+		this.contextRunner
+				.withUserConfiguration(WithoutTestFilterConfig.class,
+						OnMissingWithValueConfig.class)
+				.run((context) -> assertThat(context)
+						.satisfies(filterBeanRequirement("myOtherFilter", "testFilter")));
+	}
+
+	@Test
+	public void outcomeWhenValueIsOfExistingBeanReturnsNoMatch() {
+		this.contextRunner
+				.withUserConfiguration(WithTestFilterConfig.class,
+						OnMissingWithValueConfig.class)
+				.run((context) -> assertThat(context)
+						.satisfies(filterBeanRequirement("myTestFilter")));
+	}
+
+	@Test
+	public void outcomeWhenValueIsOfMissingBeanRegistrationReturnsMatch() {
+		this.contextRunner
+				.withUserConfiguration(WithoutTestFilterRegistrationConfig.class,
+						OnMissingWithValueConfig.class)
+				.run((context) -> assertThat(context)
+						.satisfies(filterBeanRequirement("myOtherFilter", "testFilter")));
+	}
+
+	@Test
+	public void outcomeWhenValueIsOfExistingBeanRegistrationReturnsNoMatch() {
+		this.contextRunner
+				.withUserConfiguration(WithTestFilterRegistrationConfig.class,
+						OnMissingWithValueConfig.class)
+				.run((context) -> assertThat(context)
+						.satisfies(filterBeanRequirement("myTestFilter")));
+	}
+
+	@Test
+	public void outcomeWhenReturnTypeIsOfExistingBeanReturnsNoMatch() {
+		this.contextRunner
+				.withUserConfiguration(WithTestFilterConfig.class,
+						OnMissingWithReturnTypeConfig.class)
+				.run((context) -> assertThat(context)
+						.satisfies(filterBeanRequirement("myTestFilter")));
+	}
+
+	@Test
+	public void outcomeWhenReturnTypeIsOfExistingBeanRegistrationReturnsNoMatch() {
+		this.contextRunner
+				.withUserConfiguration(WithTestFilterRegistrationConfig.class,
+						OnMissingWithReturnTypeConfig.class)
+				.run((context) -> assertThat(context)
+						.satisfies(filterBeanRequirement("myTestFilter")));
+	}
+
+	@Test
+	public void outcomeWhenReturnRegistrationTypeIsOfExistingBeanReturnsNoMatch() {
+		this.contextRunner
+				.withUserConfiguration(WithTestFilterConfig.class,
+						OnMissingWithReturnRegistrationTypeConfig.class)
+				.run((context) -> assertThat(context)
+						.satisfies(filterBeanRequirement("myTestFilter")));
+	}
+
+	@Test
+	public void outcomeWhenReturnRegistrationTypeIsOfExistingBeanRegistrationReturnsNoMatch() {
+		this.contextRunner
+				.withUserConfiguration(WithTestFilterRegistrationConfig.class,
+						OnMissingWithReturnRegistrationTypeConfig.class)
+				.run((context) -> assertThat(context)
+						.satisfies(filterBeanRequirement("myTestFilter")));
+	}
+
+	private Consumer<ConfigurableApplicationContext> filterBeanRequirement(
+			String... names) {
+		return (context) -> {
+			String[] filters = context.getBeanNamesForType(Filter.class);
+			String[] registrations = context
+					.getBeanNamesForType(FilterRegistrationBean.class);
+			assertThat(StringUtils.concatenateStringArrays(filters, registrations))
+					.containsOnly(names);
+		};
+	}
+
+	@Configuration
+	static class WithTestFilterConfig {
+
+		@Bean
+		public TestFilter myTestFilter() {
+			return new TestFilter();
+		}
+
+	}
+
+	@Configuration
+	static class WithoutTestFilterConfig {
+
+		@Bean
+		public OtherFilter myOtherFilter() {
+			return new OtherFilter();
+		}
+
+	}
+
+	@Configuration
+	static class WithoutTestFilterRegistrationConfig {
+
+		@Bean
+		public FilterRegistrationBean<OtherFilter> myOtherFilter() {
+			return new FilterRegistrationBean<OtherFilter>(new OtherFilter());
+		}
+
+	}
+
+	@Configuration
+	static class WithTestFilterRegistrationConfig {
+
+		@Bean
+		public FilterRegistrationBean<TestFilter> myTestFilter() {
+			return new FilterRegistrationBean<TestFilter>(new TestFilter());
+		}
+
+	}
+
+	@Configuration
+	static class OnMissingWithValueConfig {
+
+		@Bean
+		@ConditionalOnMissingFilterBean(TestFilter.class)
+		public TestFilter testFilter() {
+			return new TestFilter();
+		}
+
+	}
+
+	@Configuration
+	static class OnMissingWithReturnTypeConfig {
+
+		@Bean
+		@ConditionalOnMissingFilterBean
+		public TestFilter testFilter() {
+			return new TestFilter();
+		}
+
+	}
+
+	@Configuration
+	static class OnMissingWithReturnRegistrationTypeConfig {
+
+		@Bean
+		@ConditionalOnMissingFilterBean
+		public FilterRegistrationBean<TestFilter> testFilter() {
+			return new FilterRegistrationBean<TestFilter>(new TestFilter());
+		}
+
+	}
+
+	static class TestFilter implements Filter {
+
+		@Override
+		public void doFilter(ServletRequest request, ServletResponse response,
+				FilterChain chain) throws IOException, ServletException {
+		}
+
+	}
+
+	static class OtherFilter implements Filter {
+
+		@Override
+		public void doFilter(ServletRequest request, ServletResponse response,
+				FilterChain chain) throws IOException, ServletException {
+		}
+
+	}
+
+}