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/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

@@ -0,0 +1,49 @@
+/*
+ * 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;
+	}
+
+}