YamlProcessor embraces SnakeYAML 1.18+ duplicate key handling

Includes removal of StrictMapAppenderConstructor for compatibility with SnakeYAML 1.21.

Issue: SPR-16791

spring-beans/spring-beans.gradle

@@ -5,7 +5,7 @@ apply plugin: "groovy"
 dependencies {
 	compile(project(':spring-core'))
 	optional("javax.inject:javax.inject:1")
-	optional("org.yaml:snakeyaml:1.20")
+	optional("org.yaml:snakeyaml:1.21")
     optional("org.codehaus.groovy:groovy-all:${groovyVersion}")
 	optional("org.jetbrains.kotlin:kotlin-reflect:${kotlinVersion}")
 	optional("org.jetbrains.kotlin:kotlin-stdlib:${kotlinVersion}")

spring-beans/src/main/java/org/springframework/beans/factory/config/YamlMapFactoryBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -64,6 +64,8 @@ import org.springframework.lang.Nullable;
  * Note that the value of "foo" in the first document is not simply replaced
  * with the value in the second, but its nested values are merged.
  *
+ * <p>Requires SnakeYAML 1.18 or higher, as of Spring Framework 5.0.6.
+ *
  * @author Dave Syer
  * @author Juergen Hoeller
  * @since 4.1

spring-beans/src/main/java/org/springframework/beans/factory/config/YamlProcessor.java

@@ -18,7 +18,6 @@ package org.springframework.beans.factory.config;
 
 import java.io.IOException;
 import java.io.Reader;
-import java.util.AbstractMap;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
@@ -26,14 +25,11 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
-import java.util.Set;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.yaml.snakeyaml.LoaderOptions;
 import org.yaml.snakeyaml.Yaml;
-import org.yaml.snakeyaml.constructor.Constructor;
-import org.yaml.snakeyaml.nodes.MappingNode;
-import org.yaml.snakeyaml.parser.ParserException;
 import org.yaml.snakeyaml.reader.UnicodeReader;
 
 import org.springframework.core.CollectionFactory;
@@ -45,6 +41,8 @@ import org.springframework.util.StringUtils;
 /**
  * Base class for YAML factories.
  *
+ * <p>Requires SnakeYAML 1.18 or higher, as of Spring Framework 5.0.6.
+ *
  * @author Dave Syer
  * @author Juergen Hoeller
  * @since 4.1
@@ -144,9 +142,14 @@ public abstract class YamlProcessor {
 
 	/**
 	 * Create the {@link Yaml} instance to use.
+	 * <p>The default implementation sets the "allowDuplicateKeys" flag to {@code false},
+	 * enabling built-in duplicate key handling in SnakeYAML 1.18+.
+	 * @see LoaderOptions#setAllowDuplicateKeys(boolean)
 	 */
 	protected Yaml createYaml() {
-		return new Yaml(new StrictMapAppenderConstructor());
+		LoaderOptions options = new LoaderOptions();
+		options.setAllowDuplicateKeys(false);
+		return new Yaml(options);
 	}
 
 	private boolean process(MatchCallback callback, Yaml yaml, Resource resource) {
@@ -390,45 +393,4 @@ public abstract class YamlProcessor {
 		FIRST_FOUND
 	}
 
-
-	/**
-	 * A specialized {@link Constructor} that checks for duplicate keys.
-	 */
-	protected static class StrictMapAppenderConstructor extends Constructor {
-
-		// Declared as public for use in subclasses
-		public StrictMapAppenderConstructor() {
-			super();
-		}
-
-		@Override
-		protected Map<Object, Object> constructMapping(MappingNode node) {
-			try {
-				return super.constructMapping(node);
-			}
-			catch (IllegalStateException ex) {
-				throw new ParserException("while parsing MappingNode",
-						node.getStartMark(), ex.getMessage(), node.getEndMark());
-			}
-		}
-
-		@Override
-		protected Map<Object, Object> createDefaultMap() {
-			final Map<Object, Object> delegate = super.createDefaultMap();
-			return new AbstractMap<Object, Object>() {
-				@Override
-				public Object put(Object key, Object value) {
-					if (delegate.containsKey(key)) {
-						throw new IllegalStateException("Duplicate key: " + key);
-					}
-					return delegate.put(key, value);
-				}
-				@Override
-				public Set<Entry<Object, Object>> entrySet() {
-					return delegate.entrySet();
-				}
-			};
-		}
-	}
-
 }

spring-beans/src/main/java/org/springframework/beans/factory/config/YamlPropertiesFactoryBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -74,6 +74,8 @@ import org.springframework.lang.Nullable;
  * servers[1]=foo.bar.com
  * </pre>
  *
+ * <p>Requires SnakeYAML 1.18 or higher, as of Spring Framework 5.0.6.
+ *
  * @author Dave Syer
  * @author Stephane Nicoll
  * @author Juergen Hoeller

spring-beans/src/test/java/org/springframework/beans/factory/config/YamlMapFactoryBeanTests.java

@@ -19,10 +19,10 @@ package org.springframework.beans.factory.config;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.LinkedHashMap;
-import java.util.List;
 import java.util.Map;
 
 import org.junit.Test;
+import org.yaml.snakeyaml.constructor.DuplicateKeyException;
 
 import org.springframework.core.io.AbstractResource;
 import org.springframework.core.io.ByteArrayResource;
@@ -42,27 +42,27 @@ public class YamlMapFactoryBeanTests {
 
 
 	@Test
-	public void testSetIgnoreResourceNotFound() throws Exception {
+	public void testSetIgnoreResourceNotFound() {
 		this.factory.setResolutionMethod(YamlMapFactoryBean.ResolutionMethod.OVERRIDE_AND_IGNORE);
 		this.factory.setResources(new FileSystemResource("non-exsitent-file.yml"));
 		assertEquals(0, this.factory.getObject().size());
 	}
 
 	@Test(expected = IllegalStateException.class)
-	public void testSetBarfOnResourceNotFound() throws Exception {
+	public void testSetBarfOnResourceNotFound() {
 		this.factory.setResources(new FileSystemResource("non-exsitent-file.yml"));
 		assertEquals(0, this.factory.getObject().size());
 	}
 
 	@Test
-	public void testGetObject() throws Exception {
+	public void testGetObject() {
 		this.factory.setResources(new ByteArrayResource("foo: bar".getBytes()));
 		assertEquals(1, this.factory.getObject().size());
 	}
 
 	@SuppressWarnings("unchecked")
 	@Test
-	public void testOverrideAndRemoveDefaults() throws Exception {
+	public void testOverrideAndRemoveDefaults() {
 		this.factory.setResources(new ByteArrayResource("foo:\n  bar: spam".getBytes()),
 				new ByteArrayResource("foo:\n  spam: bar".getBytes()));
 
@@ -71,7 +71,7 @@ public class YamlMapFactoryBeanTests {
 	}
 
 	@Test
-	public void testFirstFound() throws Exception {
+	public void testFirstFound() {
 		this.factory.setResolutionMethod(YamlProcessor.ResolutionMethod.FIRST_FOUND);
 		this.factory.setResources(new AbstractResource() {
 			@Override
@@ -88,7 +88,7 @@ public class YamlMapFactoryBeanTests {
 	}
 
 	@Test
-	public void testMapWithPeriodsInKey() throws Exception {
+	public void testMapWithPeriodsInKey() {
 		this.factory.setResources(new ByteArrayResource("foo:\n  ? key1.key2\n  : value".getBytes()));
 		Map<String, Object> map = this.factory.getObject();
 
@@ -103,7 +103,7 @@ public class YamlMapFactoryBeanTests {
 	}
 
 	@Test
-	public void testMapWithIntegerValue() throws Exception {
+	public void testMapWithIntegerValue() {
 		this.factory.setResources(new ByteArrayResource("foo:\n  ? key1.key2\n  : 3".getBytes()));
 		Map<String, Object> map = this.factory.getObject();
 
@@ -117,33 +117,10 @@ public class YamlMapFactoryBeanTests {
 		assertEquals(Integer.valueOf(3), sub.get("key1.key2"));
 	}
 
-	@Test
-	public void mapWithEmptyArrayValue() {
-		this.factory.setResources(new ByteArrayResource("a: alpha\ntest: []".getBytes()));
-		assertTrue(this.factory.getObject().containsKey("test"));
-		assertEquals(((List<?>)this.factory.getObject().get("test")).size(), 0);
-	}
-
-	@Test
-	public void mapWithEmptyValue() {
-		this.factory.setResources(new ByteArrayResource("a: alpha\ntest:".getBytes()));
-		assertTrue(this.factory.getObject().containsKey("test"));
-		assertNull(this.factory.getObject().get("test"));
-	}
-
-	@Test
-	public void testDuplicateKey() throws Exception {
+	@Test(expected = DuplicateKeyException.class)
+	public void testDuplicateKey() {
 		this.factory.setResources(new ByteArrayResource("mymap:\n  foo: bar\nmymap:\n  bar: foo".getBytes()));
-		Map<String, Object> map = this.factory.getObject();
-
-		assertEquals(1, map.size());
-		assertTrue(map.containsKey("mymap"));
-		Object object = map.get("mymap");
-		assertTrue(object instanceof LinkedHashMap);
-		@SuppressWarnings("unchecked")
-		Map<String, Object> sub = (Map<String, Object>) object;
-		assertEquals(1, sub.size());
-		assertEquals("foo", sub.get("bar"));
+		this.factory.getObject().get("mymap");
 	}
 
 }

spring-beans/src/test/java/org/springframework/beans/factory/config/YamlProcessorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -18,7 +18,6 @@ package org.springframework.beans.factory.config;
 
 import java.util.LinkedHashMap;
 import java.util.Map;
-import java.util.Properties;
 
 import org.junit.Rule;
 import org.junit.Test;
@@ -29,7 +28,6 @@ import org.yaml.snakeyaml.scanner.ScannerException;
 import org.springframework.core.io.ByteArrayResource;
 
 import static org.junit.Assert.*;
-import static org.springframework.beans.factory.config.YamlProcessor.*;
 
 /**
  * Tests for {@link YamlProcessor}.
@@ -48,91 +46,65 @@ public class YamlProcessorTests {
 	@Test
 	public void arrayConvertedToIndexedBeanReference() {
 		this.processor.setResources(new ByteArrayResource("foo: bar\nbar: [1,2,3]".getBytes()));
-		this.processor.process(new MatchCallback() {
-			@Override
-			public void process(Properties properties, Map<String, Object> map) {
-				assertEquals(4, properties.size());
-				assertEquals("bar", properties.get("foo"));
-				assertEquals("bar", properties.getProperty("foo"));
-				assertEquals(1, properties.get("bar[0]"));
-				assertEquals("1", properties.getProperty("bar[0]"));
-				assertEquals(2, properties.get("bar[1]"));
-				assertEquals("2", properties.getProperty("bar[1]"));
-				assertEquals(3, properties.get("bar[2]"));
-				assertEquals("3", properties.getProperty("bar[2]"));
-			}
+		this.processor.process((properties, map) -> {
+			assertEquals(4, properties.size());
+			assertEquals("bar", properties.get("foo"));
+			assertEquals("bar", properties.getProperty("foo"));
+			assertEquals(1, properties.get("bar[0]"));
+			assertEquals("1", properties.getProperty("bar[0]"));
+			assertEquals(2, properties.get("bar[1]"));
+			assertEquals("2", properties.getProperty("bar[1]"));
+			assertEquals(3, properties.get("bar[2]"));
+			assertEquals("3", properties.getProperty("bar[2]"));
 		});
 	}
 
 	@Test
-	public void testStringResource() throws Exception {
+	public void testStringResource() {
 		this.processor.setResources(new ByteArrayResource("foo # a document that is a literal".getBytes()));
-		this.processor.process(new MatchCallback() {
-			@Override
-			public void process(Properties properties, Map<String, Object> map) {
-				assertEquals("foo", map.get("document"));
-			}
-		});
+		this.processor.process((properties, map) -> assertEquals("foo", map.get("document")));
 	}
 
 	@Test
-	public void testBadDocumentStart() throws Exception {
+	public void testBadDocumentStart() {
 		this.processor.setResources(new ByteArrayResource("foo # a document\nbar: baz".getBytes()));
 		this.exception.expect(ParserException.class);
 		this.exception.expectMessage("line 2, column 1");
-		this.processor.process(new MatchCallback() {
-			@Override
-			public void process(Properties properties, Map<String, Object> map) {
-			}
-		});
+		this.processor.process((properties, map) -> {});
 	}
 
 	@Test
-	public void testBadResource() throws Exception {
+	public void testBadResource() {
 		this.processor.setResources(new ByteArrayResource("foo: bar\ncd\nspam:\n  foo: baz".getBytes()));
 		this.exception.expect(ScannerException.class);
 		this.exception.expectMessage("line 3, column 1");
-		this.processor.process(new MatchCallback() {
-			@Override
-			public void process(Properties properties, Map<String, Object> map) {
-			}
-		});
+		this.processor.process((properties, map) -> {});
 	}
 
 	@Test
 	public void mapConvertedToIndexedBeanReference() {
 		this.processor.setResources(new ByteArrayResource("foo: bar\nbar:\n spam: bucket".getBytes()));
-		this.processor.process(new MatchCallback() {
-			@Override
-			public void process(Properties properties, Map<String, Object> map) {
-				// System.err.println(properties);
-				assertEquals("bucket", properties.get("bar.spam"));
-				assertEquals(2, properties.size());
-			}
+		this.processor.process((properties, map) -> {
+			assertEquals("bucket", properties.get("bar.spam"));
+			assertEquals(2, properties.size());
 		});
 	}
 
 	@Test
 	public void integerKeyBehaves() {
 		this.processor.setResources(new ByteArrayResource("foo: bar\n1: bar".getBytes()));
-		this.processor.process(new MatchCallback() {
-			@Override
-			public void process(Properties properties, Map<String, Object> map) {
-				assertEquals("bar", properties.get("[1]"));
-				assertEquals(2, properties.size());
-			}
+		this.processor.process((properties, map) -> {
+			assertEquals("bar", properties.get("[1]"));
+			assertEquals(2, properties.size());
 		});
 	}
 
 	@Test
 	public void integerDeepKeyBehaves() {
 		this.processor.setResources(new ByteArrayResource("foo:\n  1: bar".getBytes()));
-		this.processor.process(new MatchCallback() {
-			@Override
-			public void process(Properties properties, Map<String, Object> map) {
-				assertEquals("bar", properties.get("foo[1]"));
-				assertEquals(1, properties.size());
-			}
+		this.processor.process((properties, map) -> {
+			assertEquals("bar", properties.get("foo[1]"));
+			assertEquals(1, properties.size());
 		});
 	}
 
@@ -140,18 +112,15 @@ public class YamlProcessorTests {
 	@SuppressWarnings("unchecked")
 	public void flattenedMapIsSameAsPropertiesButOrdered() {
 		this.processor.setResources(new ByteArrayResource("foo: bar\nbar:\n spam: bucket".getBytes()));
-		this.processor.process(new MatchCallback() {
-			@Override
-			public void process(Properties properties, Map<String, Object> map) {
-				assertEquals("bucket", properties.get("bar.spam"));
-				assertEquals(2, properties.size());
-				Map<String, Object> flattenedMap = processor.getFlattenedMap(map);
-				assertEquals("bucket", flattenedMap.get("bar.spam"));
-				assertEquals(2, flattenedMap.size());
-				assertTrue(flattenedMap instanceof LinkedHashMap);
-				Map<String, Object> bar = (Map<String, Object>) map.get("bar");
-				assertEquals("bucket", bar.get("spam"));
-			}
+		this.processor.process((properties, map) -> {
+			assertEquals("bucket", properties.get("bar.spam"));
+			assertEquals(2, properties.size());
+			Map<String, Object> flattenedMap = processor.getFlattenedMap(map);
+			assertEquals("bucket", flattenedMap.get("bar.spam"));
+			assertEquals(2, flattenedMap.size());
+			assertTrue(flattenedMap instanceof LinkedHashMap);
+			Map<String, Object> bar = (Map<String, Object>) map.get("bar");
+			assertEquals("bucket", bar.get("spam"));
 		});
 	}
 

spring-beans/src/test/java/org/springframework/beans/factory/config/YamlPropertiesFactoryBeanTests.java

@@ -19,11 +19,11 @@ package org.springframework.beans.factory.config;
 import java.util.Map;
 import java.util.Properties;
 
-import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 import org.yaml.snakeyaml.Yaml;
+import org.yaml.snakeyaml.constructor.DuplicateKeyException;
 import org.yaml.snakeyaml.scanner.ScannerException;
 
 import org.springframework.core.io.ByteArrayResource;
@@ -46,17 +46,16 @@ public class YamlPropertiesFactoryBeanTests {
 
 
 	@Test
-	public void testLoadResource() throws Exception {
+	public void testLoadResource() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
-		factory.setResources(new ByteArrayResource(
-				"foo: bar\nspam:\n  foo: baz".getBytes()));
+		factory.setResources(new ByteArrayResource("foo: bar\nspam:\n  foo: baz".getBytes()));
 		Properties properties = factory.getObject();
 		assertThat(properties.getProperty("foo"), equalTo("bar"));
 		assertThat(properties.getProperty("spam.foo"), equalTo("baz"));
 	}
 
 	@Test
-	public void testBadResource() throws Exception {
+	public void testBadResource() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setResources(new ByteArrayResource(
 				"foo: bar\ncd\nspam:\n  foo: baz".getBytes()));
@@ -66,7 +65,7 @@ public class YamlPropertiesFactoryBeanTests {
 	}
 
 	@Test
-	public void testLoadResourcesWithOverride() throws Exception {
+	public void testLoadResourcesWithOverride() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setResources(
 				new ByteArrayResource("foo: bar\nspam:\n  foo: baz".getBytes()),
@@ -77,27 +76,24 @@ public class YamlPropertiesFactoryBeanTests {
 		assertThat(properties.getProperty("foo.bar"), equalTo("spam"));
 	}
 
-	@Test
-	public void testLoadResourcesWithInternalOverride() throws Exception {
+	@Test(expected = DuplicateKeyException.class)
+	public void testLoadResourcesWithInternalOverride() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setResources(new ByteArrayResource(
 				"foo: bar\nspam:\n  foo: baz\nfoo: bucket".getBytes()));
-		Properties properties = factory.getObject();
-		assertThat(properties.getProperty("foo"), equalTo("bucket"));
+		factory.getObject();
 	}
 
-	@Test
-	@Ignore("We can't fail on duplicate keys because the Map is created by the YAML library")
-	public void testLoadResourcesWithNestedInternalOverride() throws Exception {
+	@Test(expected = DuplicateKeyException.class)
+	public void testLoadResourcesWithNestedInternalOverride() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setResources(new ByteArrayResource(
 				"foo:\n  bar: spam\n  foo: baz\nbreak: it\nfoo: bucket".getBytes()));
-		Properties properties = factory.getObject();
-		assertThat(properties.getProperty("foo.bar"), equalTo("spam"));
+		factory.getObject();
 	}
 
 	@Test
-	public void testLoadResourceWithMultipleDocuments() throws Exception {
+	public void testLoadResourceWithMultipleDocuments() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setResources(new ByteArrayResource(
 				"foo: bar\nspam: baz\n---\nfoo: bag".getBytes()));
@@ -107,37 +103,29 @@ public class YamlPropertiesFactoryBeanTests {
 	}
 
 	@Test
-	public void testLoadResourceWithSelectedDocuments() throws Exception {
+	public void testLoadResourceWithSelectedDocuments() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setResources(new ByteArrayResource(
 				"foo: bar\nspam: baz\n---\nfoo: bag\nspam: bad".getBytes()));
-		factory.setDocumentMatchers(new DocumentMatcher() {
-			@Override
-			public MatchStatus matches(Properties properties) {
-				return ("bag".equals(properties.getProperty("foo")) ?
-						MatchStatus.FOUND : MatchStatus.NOT_FOUND);
-			}
-		});
+		factory.setDocumentMatchers((DocumentMatcher) properties -> ("bag".equals(properties.getProperty("foo")) ?
+				MatchStatus.FOUND : MatchStatus.NOT_FOUND));
 		Properties properties = factory.getObject();
 		assertThat(properties.getProperty("foo"), equalTo("bag"));
 		assertThat(properties.getProperty("spam"), equalTo("bad"));
 	}
 
 	@Test
-	public void testLoadResourceWithDefaultMatch() throws Exception {
+	public void testLoadResourceWithDefaultMatch() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setMatchDefault(true);
 		factory.setResources(new ByteArrayResource(
 				"one: two\n---\nfoo: bar\nspam: baz\n---\nfoo: bag\nspam: bad".getBytes()));
-		factory.setDocumentMatchers(new DocumentMatcher() {
-			@Override
-			public MatchStatus matches(Properties properties) {
-				if (!properties.containsKey("foo")) {
-					return MatchStatus.ABSTAIN;
-				}
-				return ("bag".equals(properties.getProperty("foo")) ?
-						MatchStatus.FOUND : MatchStatus.NOT_FOUND);
+		factory.setDocumentMatchers((DocumentMatcher) properties -> {
+			if (!properties.containsKey("foo")) {
+				return MatchStatus.ABSTAIN;
 			}
+			return ("bag".equals(properties.getProperty("foo")) ?
+					MatchStatus.FOUND : MatchStatus.NOT_FOUND);
 		});
 		Properties properties = factory.getObject();
 		assertThat(properties.getProperty("foo"), equalTo("bag"));
@@ -146,7 +134,7 @@ public class YamlPropertiesFactoryBeanTests {
 	}
 
 	@Test
-	public void testLoadResourceWithoutDefaultMatch() throws Exception {
+	public void testLoadResourceWithoutDefaultMatch() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setMatchDefault(false);
 		factory.setResources(new ByteArrayResource(
@@ -168,20 +156,17 @@ public class YamlPropertiesFactoryBeanTests {
 	}
 
 	@Test
-	public void testLoadResourceWithDefaultMatchSkippingMissedMatch() throws Exception {
+	public void testLoadResourceWithDefaultMatchSkippingMissedMatch() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setMatchDefault(true);
 		factory.setResources(new ByteArrayResource(
 				"one: two\n---\nfoo: bag\nspam: bad\n---\nfoo: bar\nspam: baz".getBytes()));
-		factory.setDocumentMatchers(new DocumentMatcher() {
-			@Override
-			public MatchStatus matches(Properties properties) {
-				if (!properties.containsKey("foo")) {
-					return MatchStatus.ABSTAIN;
-				}
-				return ("bag".equals(properties.getProperty("foo")) ?
-						MatchStatus.FOUND : MatchStatus.NOT_FOUND);
+		factory.setDocumentMatchers((DocumentMatcher) properties -> {
+			if (!properties.containsKey("foo")) {
+				return MatchStatus.ABSTAIN;
 			}
+			return ("bag".equals(properties.getProperty("foo")) ?
+					MatchStatus.FOUND : MatchStatus.NOT_FOUND);
 		});
 		Properties properties = factory.getObject();
 		assertThat(properties.getProperty("foo"), equalTo("bag"));
@@ -190,7 +175,7 @@ public class YamlPropertiesFactoryBeanTests {
 	}
 
 	@Test
-	public void testLoadNonExistentResource() throws Exception {
+	public void testLoadNonExistentResource() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setResolutionMethod(ResolutionMethod.OVERRIDE_AND_IGNORE);
 		factory.setResources(new ClassPathResource("no-such-file.yml"));
@@ -199,7 +184,7 @@ public class YamlPropertiesFactoryBeanTests {
 	}
 
 	@Test
-	public void testLoadNull() throws Exception {
+	public void testLoadNull() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setResources(new ByteArrayResource("foo: bar\nspam:".getBytes()));
 		Properties properties = factory.getObject();
@@ -217,7 +202,7 @@ public class YamlPropertiesFactoryBeanTests {
 	}
 
 	@Test
-	public void testLoadArrayOfString() throws Exception {
+	public void testLoadArrayOfString() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setResources(new ByteArrayResource("foo:\n- bar\n- baz".getBytes()));
 		Properties properties = factory.getObject();
@@ -227,7 +212,7 @@ public class YamlPropertiesFactoryBeanTests {
 	}
 
 	@Test
-	public void testLoadArrayOfInteger() throws Exception {
+	public void testLoadArrayOfInteger() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setResources(new ByteArrayResource("foo:\n- 1\n- 2".getBytes()));
 		Properties properties = factory.getObject();
@@ -237,7 +222,7 @@ public class YamlPropertiesFactoryBeanTests {
 	}
 
 	@Test
-	public void testLoadArrayOfObject() throws Exception {
+	public void testLoadArrayOfObject() {
 		YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
 		factory.setResources(new ByteArrayResource(
 				"foo:\n- bar:\n    spam: crap\n- baz\n- one: two\n  three: four".getBytes()
@@ -255,8 +240,8 @@ public class YamlPropertiesFactoryBeanTests {
 	public void testYaml() {
 		Yaml yaml = new Yaml();
 		Map<String, ?> map = yaml.loadAs("foo: bar\nspam:\n  foo: baz", Map.class);
-		assertThat(map.get("foo"), equalTo((Object) "bar"));
-		assertThat(((Map<String, Object>) map.get("spam")).get("foo"), equalTo((Object) "baz"));
+		assertThat(map.get("foo"), equalTo("bar"));
+		assertThat(((Map<String, Object>) map.get("spam")).get("foo"), equalTo("baz"));
 	}
 
 }