Introduce ConfigurableConversionService interface

Consolidates ConversionService and ConverterRegistry interfaces;
implemented by GenericConversionService.

ConfigurablePropertyResolver#getConversionService now returns this
new type (hence so too does
ConfigurableEnvironment#getConversionService). This allows for
convenient addition / removal of Converter instances from Environment's
existing ConversionService.  For example:

    ConfigurableApplicationContext ctx = new ...
    ConfigurableEnvironment env = ctx.getEnvironment();
    env.getConversionService().addConverter(new FooConverter());

Issue: SPR-8389

org.springframework.core/src/main/java/org/springframework/core/convert/support/ConfigurableConversionService.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2002-2011 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.core.convert.support;
+
+import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.converter.ConverterRegistry;
+
+/**
+ * Configuration interface to be implemented by most if not all {@link ConversionService}
+ * types. Consolidates the read-only operations exposed by {@link ConversionService} and
+ * the mutating operations of {@link ConverterRegistry} to allow for convenient ad-hoc
+ * addition and removal of {@link org.springframework.core.convert.converter.Converter
+ * Converters} through. The latter is particularly useful when working against a
+ * {@link org.springframework.core.env.ConfigurableEnvironment ConfigurableEnvironment}
+ * instance in application context bootstrapping code.
+ *
+ * @author Chris Beams
+ * @since 3.1
+ * @see org.springframework.core.env.ConfigurablePropertyResolver#getConversionService()
+ * @see org.springframework.core.env.ConfigurableEnvironment
+ * @see org.springframework.context.ConfigurableApplicationContext#getEnvironment()
+ */
+public interface ConfigurableConversionService extends ConversionService, ConverterRegistry {
+
+}

org.springframework.core/src/main/java/org/springframework/core/convert/support/GenericConversionService.java

@@ -47,13 +47,15 @@ import org.springframework.util.ClassUtils;
 
 /**
  * Base {@link ConversionService} implementation suitable for use in most environments.
- * Implements {@link ConverterRegistry} as registration API.
+ * Indirectly implements {@link ConverterRegistry} as registration API through the
+ * {@link ConfigurableConversionService} interface.
  *
  * @author Keith Donald
  * @author Juergen Hoeller
+ * @author Chris Beams
  * @since 3.0
  */
-public class GenericConversionService implements ConversionService, ConverterRegistry {
+public class GenericConversionService implements ConfigurableConversionService {
 
 	private static final GenericConverter NO_OP_CONVERTER = new GenericConverter() {
 		public Set<ConvertiblePair> getConvertibleTypes() {

org.springframework.core/src/main/java/org/springframework/core/env/AbstractEnvironment.java

@@ -29,7 +29,7 @@ import java.util.Set;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.support.ConfigurableConversionService;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -356,11 +356,11 @@ public abstract class AbstractEnvironment implements ConfigurableEnvironment {
 		return this.propertyResolver.resolveRequiredPlaceholders(text);
 	}
 
-	public void setConversionService(ConversionService conversionService) {
+	public void setConversionService(ConfigurableConversionService conversionService) {
 		this.propertyResolver.setConversionService(conversionService);
 	}
 
-	public ConversionService getConversionService() {
+	public ConfigurableConversionService getConversionService() {
 		return this.propertyResolver.getConversionService();
 	}
 

org.springframework.core/src/main/java/org/springframework/core/env/AbstractPropertyResolver.java

@@ -26,7 +26,7 @@ import java.util.Set;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.support.ConfigurableConversionService;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.util.PropertyPlaceholderHelper;
 import org.springframework.util.PropertyPlaceholderHelper.PlaceholderResolver;
@@ -41,7 +41,7 @@ public abstract class AbstractPropertyResolver implements ConfigurablePropertyRe
 
 	protected final Log logger = LogFactory.getLog(getClass());
 
-	protected ConversionService conversionService = new DefaultConversionService();
+	protected ConfigurableConversionService conversionService = new DefaultConversionService();
 
 	private PropertyPlaceholderHelper nonStrictHelper;
 	private PropertyPlaceholderHelper strictHelper;
@@ -52,11 +52,11 @@ public abstract class AbstractPropertyResolver implements ConfigurablePropertyRe
 
 	private final Set<String> requiredProperties = new LinkedHashSet<String>();
 
-	public ConversionService getConversionService() {
+	public ConfigurableConversionService getConversionService() {
 		return this.conversionService;
 	}
 
-	public void setConversionService(ConversionService conversionService) {
+	public void setConversionService(ConfigurableConversionService conversionService) {
 		this.conversionService = conversionService;
 	}
 

org.springframework.core/src/main/java/org/springframework/core/env/ConfigurablePropertyResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 the original author or authors.
+ * Copyright 2002-2011 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.
@@ -16,14 +16,13 @@
 
 package org.springframework.core.env;
 
-import org.springframework.core.convert.ConversionService;
-
+import org.springframework.core.convert.support.ConfigurableConversionService;
 
 /**
  * Configuration interface to be implemented by most if not all {@link PropertyResolver
  * PropertyResolvers}. Provides facilities for accessing and customizing the
- * {@link ConversionService} used when converting property values from one type to
- * another.
+ * {@link org.springframework.core.convert.ConversionService ConversionService} used when
+ * converting property values from one type to another.
  *
  * @author Chris Beams
  * @since 3.1
@@ -31,18 +30,31 @@ import org.springframework.core.convert.ConversionService;
 public interface ConfigurablePropertyResolver extends PropertyResolver {
 
 	/**
-	 * @return the {@link ConversionService} used when performing type
+	 * @return the {@link ConfigurableConversionService} used when performing type
 	 * conversions on properties.
+	 * <p>The configurable nature of the returned conversion service allows for
+	 * the convenient addition and removal of individual {@code Converter} instances:
+	 * <pre class="code">
+	 * ConfigurableConversionService cs = env.getConversionService();
+	 * cs.addConverter(new FooConverter());
+	 * </pre>
 	 * @see PropertyResolver#getProperty(String, Class)
+	 * @see org.springframework.core.convert.converter.ConverterRegistry#addConverter
 	 */
-	ConversionService getConversionService();
+	ConfigurableConversionService getConversionService();
 
 	/**
-	 * Set the {@link ConversionService} to be used when performing type
+	 * Set the {@link ConfigurableConversionService} to be used when performing type
 	 * conversions on properties.
+	 * <p><strong>Note:</strong> as an alternative to fully replacing the {@code
+	 * ConversionService}, consider adding or removing individual {@code Converter}
+	 * intstances by drilling into {@link #getConversionService()} and calling methods
+	 * such as {@code #addConverter}.
 	 * @see PropertyResolver#getProperty(String, Class)
+	 * @see #getConversionService()
+	 * @see org.springframework.core.convert.converter.ConverterRegistry#addConverter
 	 */
-	void setConversionService(ConversionService conversionService);
+	void setConversionService(ConfigurableConversionService conversionService);
 
 	/**
 	 * Set the prefix that placeholders replaced by this resolver must begin with.