Add ConditionalOnSingleCandidate
Add a new ConditionalOnSingleCandidate condition that determines if the condition should match only if autowiring by type is guaranteed to succeed. Used by auto-configuration that relies on a single candidate of a given type (for instance, the JdbcTemplate auto-configuration relies on the presence of a DataSource). Such wiring by type will succeed if only one bean of that type is present or if one matching instance is flagged "primary" amongst the candidates. ConditionalOnSingleCandidate is a basic version of ConditionalOnBean that only accepts a single type and does not determine a defaut based on its presence on a bean definition. Closes gh-1702pull/2779/merge
Stephane Nicoll
10 years ago
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/*
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* Copyright 2012-2015 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.boot.autoconfigure.condition;
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import java.lang.annotation.Documented;
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import java.lang.annotation.ElementType;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.lang.annotation.Target;
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import org.springframework.beans.factory.BeanFactory;
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import org.springframework.context.ApplicationContext;
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import org.springframework.context.annotation.Conditional;
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/**
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* {@link Conditional} that only matches when the specified bean class is already
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* contained in the {@link BeanFactory} and a single candidate can be determined.
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* <p>
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* The conditional will also match if multiple matching bean instances are already
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* contained in the {@link BeanFactory} but a primary candidate has been defined;
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* essentially, the condition match if auto-wiring a bean with the defined type
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* will succeed.
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*
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* @author Stephane Nicoll
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* @since 1.3.0
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*/
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@Target({ElementType.TYPE, ElementType.METHOD})
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@Retention(RetentionPolicy.RUNTIME)
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@Documented
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@Conditional(OnBeanCondition.class)
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public @interface ConditionalOnSingleCandidate {
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/**
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* The class type of bean that should be checked. The condition match if the class
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* specified is contained in the {@link ApplicationContext} and a primary candidate
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* exists in case of multiple instances.
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* <p>This attribute may <strong>not</strong> be used in conjunction with
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* {@link #type()}, but it may be used instead of {@link #type()}.
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* @return the class type of the bean to check
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*/
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Class<?> value() default Object.class;
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/**
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* The class type name of bean that should be checked. The condition matches if the
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* class specified is contained in the {@link ApplicationContext} and a primary
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* candidate exists in case of multiple instances.
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* <p>This attribute may <strong>not</strong> be used in conjunction with
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* {@link #value()}, but it may be used instead of {@link #value()}.
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* @return the class type name of the bean to check
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*/
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String type() default "";
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/**
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* Strategy to decide if the application context hierarchy (parent contexts) should be
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* considered.
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* @return the search strategy
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*/
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SearchStrategy search() default SearchStrategy.ALL;
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}
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@ -0,0 +1,164 @@
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/*
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* Copyright 2012-2015 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.boot.autoconfigure.condition;
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import org.junit.After;
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import org.junit.Rule;
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import org.junit.Test;
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import org.junit.rules.ExpectedException;
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import org.springframework.context.annotation.AnnotationConfigApplicationContext;
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import org.springframework.context.annotation.Bean;
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import org.springframework.context.annotation.Configuration;
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import org.springframework.context.annotation.Primary;
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import static org.hamcrest.CoreMatchers.isA;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertFalse;
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import static org.junit.Assert.assertTrue;
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/**
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* Tests for {@link ConditionalOnSingleCandidate}.
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*
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* @author Stephane Nicoll
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*/
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public class ConditionalOnSingleCandidateTests {
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@Rule
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public final ExpectedException thrown = ExpectedException.none();
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private final AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
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@After
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public void close() {
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if (this.context != null) {
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this.context.close();
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}
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}
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@Test
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public void singleCandidateNoCandidate() {
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load(OnBeanSingleCandidateConfiguration.class);
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assertFalse(this.context.containsBean("baz"));
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}
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@Test
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public void singleCandidateOneCandidate() {
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load(FooConfiguration.class,
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OnBeanSingleCandidateConfiguration.class);
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assertTrue(this.context.containsBean("baz"));
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assertEquals("foo", this.context.getBean("baz"));
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}
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@Test
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public void singleCandidateMultipleCandidates() {
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load(FooConfiguration.class, BarConfiguration.class,
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OnBeanSingleCandidateConfiguration.class);
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assertFalse(this.context.containsBean("baz"));
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}
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@Test
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public void singleCandidateMultipleCandidatesOnePrimary() {
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load(FooPrimaryConfiguration.class, BarConfiguration.class,
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OnBeanSingleCandidateConfiguration.class);
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assertTrue(this.context.containsBean("baz"));
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assertEquals("foo", this.context.getBean("baz"));
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}
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@Test
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public void singleCandidateMultipleCandidatesMultiplePrimary() {
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load(FooPrimaryConfiguration.class, BarPrimaryConfiguration.class,
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OnBeanSingleCandidateConfiguration.class);
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assertFalse(this.context.containsBean("baz"));
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}
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@Test
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public void invalidAnnotationTwoTypes() {
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thrown.expect(IllegalStateException.class);
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thrown.expectCause(isA(IllegalArgumentException.class));
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thrown.expectMessage(OnBeanSingleCandidateTwoTypesConfiguration.class.getName());
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load(OnBeanSingleCandidateTwoTypesConfiguration.class);
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}
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@Test
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public void invalidAnnotationNoType() {
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thrown.expect(IllegalStateException.class);
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thrown.expectCause(isA(IllegalArgumentException.class));
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thrown.expectMessage(OnBeanSingleCandidateNoTypeConfiguration.class.getName());
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load(OnBeanSingleCandidateNoTypeConfiguration.class);
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}
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private void load(Class<?>... classes) {
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this.context.register(classes);
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this.context.refresh();
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}
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@Configuration
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@ConditionalOnSingleCandidate(value = String.class)
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protected static class OnBeanSingleCandidateConfiguration {
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@Bean
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public String baz(String s) {
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return s;
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}
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}
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@Configuration
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@ConditionalOnSingleCandidate(value = String.class, type = "java.lang.String")
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protected static class OnBeanSingleCandidateTwoTypesConfiguration {
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}
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@Configuration
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@ConditionalOnSingleCandidate
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protected static class OnBeanSingleCandidateNoTypeConfiguration {
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}
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@Configuration
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protected static class FooConfiguration {
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@Bean
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public String foo() {
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return "foo";
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}
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}
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@Configuration
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protected static class FooPrimaryConfiguration {
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@Bean
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@Primary
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public String foo() {
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return "foo";
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}
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}
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@Configuration
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protected static class BarConfiguration {
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@Bean
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public String bar() {
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return "bar";
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}
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}
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@Configuration
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protected static class BarPrimaryConfiguration {
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@Bean
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@Primary
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public String bar() {
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return "bar";
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}
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}
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}
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