Add builder for feign clients. (#56)

Utilizes the logic from the registrar and the factory bean. The changes to them have been made minimal invasive.

Fixes gh-42

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/FeignClientBuilder.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2013-2018 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.cloud.openfeign;
+
+import org.springframework.context.ApplicationContext;
+
+/**
+ * A builder for creating Feign clients without using the {@link FeignClient} annotation.
+ * <p>
+ * This builder builds the Feign client exactly like it would be created by using the
+ * {@link FeignClient} annotation.
+ *
+ * @author Sven Döring
+ */
+public class FeignClientBuilder {
+
+	private final ApplicationContext applicationContext;
+
+	public FeignClientBuilder(final ApplicationContext applicationContext) {
+		this.applicationContext = applicationContext;
+	}
+
+	public <T> Builder<T> forType(final Class<T> type, final String name) {
+		return new Builder<>(applicationContext, type, name);
+	}
+
+	public static class Builder<T> {
+
+		private FeignClientFactoryBean feignClientFactoryBean;
+
+		private Builder(final ApplicationContext applicationContext, final Class<T> type,
+				final String name) {
+			this.feignClientFactoryBean = new FeignClientFactoryBean();
+
+			this.feignClientFactoryBean.setApplicationContext(applicationContext);
+			this.feignClientFactoryBean.setType(type);
+			this.feignClientFactoryBean.setName(FeignClientsRegistrar.getName(name));
+			// preset default values - these values resemble the default values on the
+			// FeignClient annotation
+			this.url("").path("").decode404(false).fallback(void.class)
+					.fallbackFactory(void.class);
+		}
+
+		public Builder url(final String url) {
+			this.feignClientFactoryBean.setUrl(FeignClientsRegistrar.getUrl(url));
+			return this;
+		}
+
+		public Builder path(final String path) {
+			this.feignClientFactoryBean.setPath(FeignClientsRegistrar.getPath(path));
+			return this;
+		}
+
+		public Builder decode404(final boolean decode404) {
+			this.feignClientFactoryBean.setDecode404(decode404);
+			return this;
+		}
+
+		public Builder fallback(final Class<T> fallback) {
+			FeignClientsRegistrar.validateFallback(fallback);
+			this.feignClientFactoryBean.setFallback(fallback);
+			return this;
+		}
+
+		public Builder fallbackFactory(final Class<T> fallbackFactory) {
+			FeignClientsRegistrar.validateFallbackFactory(fallbackFactory);
+			this.feignClientFactoryBean.setFallbackFactory(fallbackFactory);
+			return this;
+		}
+
+		/**
+		 * @param <T> the target type of the Feign client to be created
+		 * @return the created Feign client
+		 */
+		public <T> T build() {
+			return this.feignClientFactoryBean.getTarget();
+		}
+	}
+}

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/FeignClientFactoryBean.java

@@ -229,6 +229,14 @@ class FeignClientFactoryBean implements FactoryBean<Object>, InitializingBean,
 
 	@Override
 	public Object getObject() throws Exception {
+		return getTarget();
+	}
+
+	/**
+	 * @param <T> the target type of the Feign client
+	 * @return a {@link Feign} client created with the specified data and the context information
+	 */
+	<T> T getTarget() {
 		FeignContext context = applicationContext.getBean(FeignContext.class);
 		Feign.Builder builder = feign(context);
 
@@ -241,7 +249,7 @@ class FeignClientFactoryBean implements FactoryBean<Object>, InitializingBean,
 				url = this.name;
 			}
 			url += cleanPath();
-			return loadBalance(builder, context, new HardCodedTarget<>(this.type,
+			return (T) loadBalance(builder, context, new HardCodedTarget<>(this.type,
 					this.name, url));
 		}
 		if (StringUtils.hasText(this.url) && !this.url.startsWith("http")) {
@@ -258,7 +266,7 @@ class FeignClientFactoryBean implements FactoryBean<Object>, InitializingBean,
 			builder.client(client);
 		}
 		Targeter targeter = get(context, Targeter.class);
-		return targeter.target(this, builder, context, new HardCodedTarget<>(
+		return (T) targeter.target(this, builder, context, new HardCodedTarget<>(
 				this.type, this.name, url));
 	}
 

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/FeignClientsRegistrar.java

@@ -198,12 +198,19 @@ class FeignClientsRegistrar implements ImportBeanDefinitionRegistrar,
 		AnnotationAttributes annotation = AnnotationAttributes.fromMap(attributes);
 		// This blows up if an aliased property is overspecified
 		// FIXME annotation.getAliasedString("name", FeignClient.class, null);
+		validateFallback(annotation.getClass("fallback"));
+		validateFallbackFactory(annotation.getClass("fallbackFactory"));
+	}
+
+	static void validateFallback(final Class clazz) {
 		Assert.isTrue(
-			!annotation.getClass("fallback").isInterface(),
+			!clazz.isInterface(),
 			"Fallback class must implement the interface annotated by @FeignClient"
 		);
-		Assert.isTrue(
-			!annotation.getClass("fallbackFactory").isInterface(),
+	}
+
+	static void validateFallbackFactory(final Class clazz) {
+		Assert.isTrue(!clazz.isInterface(),
 			"Fallback factory must produce instances of fallback classes that implement the interface annotated by @FeignClient"
 		);
 	}
@@ -217,6 +224,10 @@ class FeignClientsRegistrar implements ImportBeanDefinitionRegistrar,
 			name = (String) attributes.get("value");
 		}
 		name = resolve(name);
+		return getName(name);
+	}
+
+	static String getName(String name) {
 		if (!StringUtils.hasText(name)) {
 			return "";
 		}
@@ -247,6 +258,10 @@ class FeignClientsRegistrar implements ImportBeanDefinitionRegistrar,
 
 	private String getUrl(Map<String, Object> attributes) {
 		String url = resolve((String) attributes.get("url"));
+		return getUrl(url);
+	}
+
+	static String getUrl(String url) {
 		if (StringUtils.hasText(url) && !(url.startsWith("#{") && url.contains("}"))) {
 			if (!url.contains("://")) {
 				url = "http://" + url;
@@ -263,6 +278,10 @@ class FeignClientsRegistrar implements ImportBeanDefinitionRegistrar,
 
 	private String getPath(Map<String, Object> attributes) {
 		String path = resolve((String) attributes.get("path"));
+		return getPath(path);
+	}
+
+	static String getPath(String path) {
 		if (StringUtils.hasText(path)) {
 			path = path.trim();
 			if (!path.startsWith("/")) {

spring-cloud-openfeign-core/src/test/java/org/springframework/cloud/openfeign/FeignClientBuilderTests.java

@@ -0,0 +1,158 @@
+/*
+ * Copyright 2013-2018 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.cloud.openfeign;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.nio.file.ClosedFileSystemException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.hamcrest.Matchers;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.mockito.Mockito;
+import org.springframework.cloud.openfeign.testclients.TestClient;
+import org.springframework.context.ApplicationContext;
+import org.springframework.util.ReflectionUtils;
+
+/**
+ * @author Sven Döring
+ */
+public class FeignClientBuilderTests {
+
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
+	private FeignClientBuilder feignClientBuilder;
+
+	private ApplicationContext applicationContext;
+
+	private static Object getDefaultValueFromFeignClientAnnotation(
+			final String methodName) {
+		final Method method = ReflectionUtils.findMethod(FeignClient.class, methodName);
+		return method.getDefaultValue();
+	}
+
+	private static void assertFactoryBeanField(final FeignClientBuilder.Builder builder,
+			final String fieldName, final Object expectedValue) {
+		final Field factoryBeanField = ReflectionUtils
+				.findField(FeignClientBuilder.Builder.class, "feignClientFactoryBean");
+		ReflectionUtils.makeAccessible(factoryBeanField);
+		final FeignClientFactoryBean factoryBean = (FeignClientFactoryBean) ReflectionUtils
+				.getField(factoryBeanField, builder);
+
+		final Field field = ReflectionUtils.findField(FeignClientFactoryBean.class,
+				fieldName);
+		ReflectionUtils.makeAccessible(field);
+		final Object value = ReflectionUtils.getField(field, factoryBean);
+		Assert.assertEquals("Expected value for the field '" + fieldName + "':",
+				expectedValue, value);
+	}
+
+	@Before
+	public void setUp() {
+		this.applicationContext = Mockito.mock(ApplicationContext.class);
+		this.feignClientBuilder = new FeignClientBuilder(applicationContext);
+	}
+
+	@Test
+	public void safetyCheckForNewFieldsOnTheFeignClientAnnotation() {
+		final List<String> methodNames = new ArrayList();
+		for (final Method method : FeignClient.class.getMethods()) {
+			methodNames.add(method.getName());
+		}
+		methodNames.removeAll(
+				Arrays.asList("annotationType", "value", "serviceId", "qualifier",
+						"configuration", "primary", "equals", "hashCode", "toString"));
+		Collections.sort(methodNames);
+		// If this safety check fails the Builder has to be updated.
+		// (1) Either a field was removed from the FeignClient annotation and so it has to
+		// be removed
+		// on this builder class.
+		// (2) Or a new field was added and the builder class has to be extended with this
+		// new field.
+		Assert.assertThat(methodNames, Matchers.contains("decode404", "fallback",
+				"fallbackFactory", "name", "path", "url"));
+	}
+
+	@Test
+	public void forType_preinitializedBuilder() {
+		// when:
+		final FeignClientBuilder.Builder builder = feignClientBuilder
+				.forType(FeignClientBuilderTests.class, "TestClient");
+
+		// then:
+		assertFactoryBeanField(builder, "applicationContext", applicationContext);
+		assertFactoryBeanField(builder, "type", FeignClientBuilderTests.class);
+		assertFactoryBeanField(builder, "name", "TestClient");
+
+		// and:
+		assertFactoryBeanField(builder, "url",
+				getDefaultValueFromFeignClientAnnotation("url"));
+		assertFactoryBeanField(builder, "path",
+				getDefaultValueFromFeignClientAnnotation("path"));
+		assertFactoryBeanField(builder, "decode404",
+				getDefaultValueFromFeignClientAnnotation("decode404"));
+		assertFactoryBeanField(builder, "fallback",
+				getDefaultValueFromFeignClientAnnotation("fallback"));
+		assertFactoryBeanField(builder, "fallbackFactory",
+				getDefaultValueFromFeignClientAnnotation("fallbackFactory"));
+	}
+
+	@Test
+	public void forType_allFieldsSetOnBuilder() {
+		// when:
+		final FeignClientBuilder.Builder builder = feignClientBuilder
+				.forType(FeignClientBuilderTests.class, "TestClient").decode404(true)
+				.fallback(Object.class).fallbackFactory(Object.class).path("Path/")
+				.url("Url/");
+
+		// then:
+		assertFactoryBeanField(builder, "applicationContext", applicationContext);
+		assertFactoryBeanField(builder, "type", FeignClientBuilderTests.class);
+		assertFactoryBeanField(builder, "name", "TestClient");
+
+		// and:
+		assertFactoryBeanField(builder, "url", "http://Url/");
+		assertFactoryBeanField(builder, "path", "/Path");
+		assertFactoryBeanField(builder, "decode404", true);
+		assertFactoryBeanField(builder, "fallback", Object.class);
+		assertFactoryBeanField(builder, "fallbackFactory", Object.class);
+	}
+
+	@Test
+	public void forType_build() {
+		// given:
+		Mockito.when(applicationContext.getBean(FeignContext.class))
+				.thenThrow(new ClosedFileSystemException()); // throw an unusual exception
+																// in the
+																// FeignClientFactoryBean
+		final FeignClientBuilder.Builder builder = feignClientBuilder
+				.forType(TestClient.class, "TestClient");
+
+		// expect: 'the build will fail right after calling build() with the mocked
+		// unusual exception'
+		thrown.expect(Matchers.isA(ClosedFileSystemException.class));
+		builder.build();
+	}
+}

spring-cloud-openfeign-core/src/test/java/org/springframework/cloud/openfeign/beans/FeignClientTests.java

@@ -31,8 +31,11 @@ import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
 import org.springframework.cloud.openfeign.EnableFeignClients;
 import org.springframework.cloud.openfeign.FeignClient;
+import org.springframework.cloud.openfeign.FeignClientBuilder;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
 import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -66,12 +69,24 @@ public class FeignClientTests {
 	@Autowired
 	private org.springframework.cloud.openfeign.beans.extra.TestClient extraClient;
 
+	@Qualifier("build-by-builder")
+	@Autowired
+	private TestClient buildByBuilder;
+
 	@Configuration
 	@EnableAutoConfiguration
 	@RestController
 	@EnableFeignClients
+	@Import(FeignClientBuilder.class)
 	protected static class Application {
 
+		@Bean("build-by-builder")
+		public TestClient buildByBuilder(final FeignClientBuilder feignClientBuilder) {
+			return feignClientBuilder
+					.forType(TestClient.class, "builderapp")
+					.build();
+		}
+
 		@RequestMapping(method = RequestMethod.GET, value = "/hello")
 		public Hello getHello() {
 			return new Hello("hello world 1");
@@ -112,7 +127,7 @@ public class FeignClientTests {
 	}
 
 	@Test
-	public void testAnnnotations() throws Exception {
+	public void testAnnotations() {
 		Map<String, Object> beans = this.context
 				.getBeansWithAnnotation(FeignClient.class);
 		assertTrue("Wrong clients: " + beans,
@@ -122,13 +137,31 @@ public class FeignClientTests {
 	@Test
 	public void testClient() {
 		assertNotNull("testClient was null", this.testClient);
-		assertNotNull("testClient was null", this.extraClient);
+		assertNotNull("extraClient was null", this.extraClient);
 		assertTrue("testClient is not a java Proxy",
 				Proxy.isProxyClass(this.testClient.getClass()));
 		InvocationHandler invocationHandler = Proxy.getInvocationHandler(this.testClient);
 		assertNotNull("invocationHandler was null", invocationHandler);
 	}
 
+	@Test
+	public void extraClient() {
+		assertNotNull("extraClient was null", this.extraClient);
+		assertTrue("extraClient is not a java Proxy",
+				Proxy.isProxyClass(this.extraClient.getClass()));
+		InvocationHandler invocationHandler = Proxy.getInvocationHandler(this.extraClient);
+		assertNotNull("invocationHandler was null", invocationHandler);
+	}
+
+	@Test
+	public void buildByBuilder() {
+		assertNotNull("buildByBuilder was null", this.buildByBuilder);
+		assertTrue("buildByBuilder is not a java Proxy",
+				Proxy.isProxyClass(this.buildByBuilder.getClass()));
+		InvocationHandler invocationHandler = Proxy.getInvocationHandler(this.buildByBuilder);
+		assertNotNull("invocationHandler was null", invocationHandler);
+	}
+
 	@Configuration
 	public static class TestDefaultFeignConfig {
 	}

spring-cloud-openfeign-core/src/test/java/org/springframework/cloud/openfeign/beans/TestClient.java

@@ -18,9 +18,11 @@ package org.springframework.cloud.openfeign.beans;
 
 import org.springframework.cloud.openfeign.FeignClient;
 import org.springframework.cloud.openfeign.beans.FeignClientTests.Hello;
+import org.springframework.context.annotation.Primary;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 
+@Primary
 @FeignClient(value = "localapp")
 public interface TestClient {
 	@RequestMapping(method = RequestMethod.GET, value = "/hello")