Ignore static and abstract accessors

This commit updates the annotation processor and the binder to ignore
any static or abstract method that has the characteristics of a JavaBean
accessor. As a result, no property is generated for those (invalid)
accessor and no binding occurs on them either.

Closes gh-12390

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/TypeElementMembers.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * 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.
@@ -21,6 +21,7 @@ import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import javax.annotation.processing.ProcessingEnvironment;
 import javax.lang.model.element.Element;
@@ -97,7 +98,7 @@ class TypeElementMembers {
 	}
 
 	private void processMethod(ExecutableElement method) {
-		if (method.getModifiers().contains(Modifier.PUBLIC)) {
+		if (isPublic(method)) {
 			String name = method.getSimpleName().toString();
 			if (isGetter(method) && !this.publicGetters.containsKey(name)) {
 				this.publicGetters.put(getAccessorName(name), method);
@@ -118,6 +119,13 @@ class TypeElementMembers {
 		}
 	}
 
+	private boolean isPublic(ExecutableElement method) {
+		Set<Modifier> modifiers = method.getModifiers();
+		return modifiers.contains(Modifier.PUBLIC)
+				&& !modifiers.contains(Modifier.ABSTRACT)
+				&& !modifiers.contains(Modifier.STATIC);
+	}
+
 	private ExecutableElement getMatchingSetter(List<ExecutableElement> candidates,
 			TypeMirror type) {
 		for (ExecutableElement candidate : candidates) {

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationprocessor/ConfigurationMetadataAnnotationProcessorTests.java

@@ -81,6 +81,7 @@ import org.springframework.boot.configurationsample.specific.InnerClassRootConfi
 import org.springframework.boot.configurationsample.specific.InvalidAccessorProperties;
 import org.springframework.boot.configurationsample.specific.InvalidDoubleRegistrationProperties;
 import org.springframework.boot.configurationsample.specific.SimplePojo;
+import org.springframework.boot.configurationsample.specific.StaticAccessor;
 import org.springframework.boot.configurationsample.specific.WildcardConfig;
 import org.springframework.boot.testsupport.compiler.TestCompiler;
 import org.springframework.util.FileCopyUtils;
@@ -365,6 +366,18 @@ public class ConfigurationMetadataAnnotationProcessorTests {
 				.fromSource(AnnotatedGetter.class));
 	}
 
+	@Test
+	public void staticAccessor() {
+		ConfigurationMetadata metadata = compile(StaticAccessor.class);
+		assertThat(metadata)
+				.has(Metadata.withGroup("specific").fromSource(StaticAccessor.class));
+		assertThat(metadata).has(Metadata.withProperty("specific.counter",
+				Integer.class).fromSource(StaticAccessor.class).withDefaultValue(42));
+		assertThat(metadata).doesNotHave(Metadata.withProperty("specific.name",
+				String.class).fromSource(StaticAccessor.class));
+		assertThat(metadata.getItems()).hasSize(2);
+	}
+
 	@Test
 	public void innerClassRootConfig() {
 		ConfigurationMetadata metadata = compile(InnerClassRootConfig.class);

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationsample/specific/StaticAccessor.java

+/*
+ * 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.configurationsample.specific;
+
+import org.springframework.boot.configurationsample.ConfigurationProperties;
+
+/**
+ * A property that is exposed by static accessors.
+ *
+ * @author Stephane Nicoll
+ */
+@ConfigurationProperties("specific")
+public class StaticAccessor {
+
+	private static String name;
+
+	private int counter = 42;
+
+	public static String getName() {
+		return name;
+	}
+
+	public static void setName(String name) {
+		StaticAccessor.name = name;
+	}
+
+	public int getCounter() {
+		return this.counter;
+	}
+
+	public void setCounter(int counter) {
+		this.counter = counter;
+	}
+
+}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/JavaBeanBinder.java

@@ -118,7 +118,9 @@ class JavaBeanBinder implements BeanBinder {
 		}
 
 		private boolean isCandidate(Method method) {
-			return Modifier.isPublic(method.getModifiers())
+			int modifiers = method.getModifiers();
+			return Modifier.isPublic(modifiers) && !Modifier.isAbstract(modifiers)
+					&& !Modifier.isStatic(modifiers)
 					&& !Object.class.equals(method.getDeclaringClass())
 					&& !Class.class.equals(method.getDeclaringClass());
 		}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/JavaBeanBinderTests.java

@@ -486,6 +486,18 @@ public class JavaBeanBinderTests {
 		assertThat(bean.getName()).isEqualTo("something");
 	}
 
+	@Test
+	public void bindToClassShouldIgnoreStaticAccessors() {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("foo.name", "invalid");
+		source.put("foo.counter", "42");
+		this.sources.add(source);
+		ExampleWithStaticAccessors bean = this.binder
+				.bind("foo", Bindable.of(ExampleWithStaticAccessors.class)).get();
+		assertThat(ExampleWithStaticAccessors.name).isNull();
+		assertThat(bean.getCounter()).isEqualTo(42);
+	}
+
 	public static class ExampleValueBean {
 
 		private int intValue;
@@ -845,6 +857,30 @@ public class JavaBeanBinderTests {
 
 	}
 
+	public static class ExampleWithStaticAccessors {
+
+		private static String name;
+
+		private int counter;
+
+		public static String getName() {
+			return name;
+		}
+
+		public static void setName(String name) {
+			ExampleWithStaticAccessors.name = name;
+		}
+
+		public int getCounter() {
+			return this.counter;
+		}
+
+		public void setCounter(int counter) {
+			this.counter = counter;
+		}
+
+	}
+
 	public enum ExampleEnum {
 
 		FOO_BAR,