Refactor PropertyPlaceholderConfigurer hierarchy

PropertySourcesPlaceholderConfigurer accommodates recent changes in
Environment and PropertySource APIs, e.g. no longer assuming enumerability
of property names.

PSPC reuses as much functionality as possible from
AbstractPropertyPlaceholderConfigurer, but overrides
postProcessBeanFactory() and defines its own variation on
processProperties() in order to accept a PropertyResolver rather than
a PropertySource.

AbstractPropertyPlaceholderConfigurer introduces doProcessProperties()
method to encapsulate that which is actually common, such as the
visiting of each bean definition once a StringValueResolver has been
created in the subclass.

org.springframework.context/src/test/java/org/springframework/context/support/PropertySourcesPlaceholderConfigurerTests.java

@@ -17,14 +17,20 @@
 package org.springframework.context.support;
 
 import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.CoreMatchers.nullValue;
 import static org.junit.Assert.assertThat;
 import static org.springframework.beans.factory.support.BeanDefinitionBuilder.genericBeanDefinition;
+import static org.springframework.beans.factory.support.BeanDefinitionBuilder.rootBeanDefinition;
 
 import java.util.Properties;
 
 import org.junit.Test;
+import org.springframework.beans.factory.BeanDefinitionStoreException;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.core.env.DefaultEnvironment;
 import org.springframework.core.env.MutablePropertySources;
+import org.springframework.core.env.PropertySource;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
 import org.springframework.mock.env.MockEnvironment;
@@ -139,6 +145,58 @@ public class PropertySourcesPlaceholderConfigurerTests {
 		assertThat(bf.getBean(TestBean.class).getName(), equalTo("${my.name}"));
 	}
 
+	@Test(expected=BeanDefinitionStoreException.class)
+	public void ignoreUnresolvablePlaceholders_falseIsDefault() {
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.registerBeanDefinition("testBean",
+				genericBeanDefinition(TestBean.class)
+					.addPropertyValue("name", "${my.name}")
+					.getBeanDefinition());
+
+		PropertySourcesPlaceholderConfigurer pc = new PropertySourcesPlaceholderConfigurer();
+		//pc.setIgnoreUnresolvablePlaceholders(false); // the default
+		pc.postProcessBeanFactory(bf); // should throw
+	}
+
+	@Test
+	public void ignoreUnresolvablePlaceholders_true() {
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.registerBeanDefinition("testBean",
+				genericBeanDefinition(TestBean.class)
+					.addPropertyValue("name", "${my.name}")
+					.getBeanDefinition());
+
+		PropertySourcesPlaceholderConfigurer pc = new PropertySourcesPlaceholderConfigurer();
+		pc.setIgnoreUnresolvablePlaceholders(true);
+		pc.postProcessBeanFactory(bf);
+		assertThat(bf.getBean(TestBean.class).getName(), equalTo("${my.name}"));
+	}
+
+	@Test
+	public void withNonEnumerablePropertySource() {
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.registerBeanDefinition("testBean",
+				genericBeanDefinition(TestBean.class)
+					.addPropertyValue("name", "${foo}")
+					.getBeanDefinition());
+
+		PropertySourcesPlaceholderConfigurer ppc = new PropertySourcesPlaceholderConfigurer();
+
+		PropertySource<?> ps = new PropertySource<Object>("simplePropertySource", new Object()) {
+			@Override
+			public Object getProperty(String key) {
+				return "bar";
+			}
+		};
+
+		MockEnvironment env = new MockEnvironment();
+		env.getPropertySources().addFirst(ps);
+		ppc.setEnvironment(env);
+
+		ppc.postProcessBeanFactory(bf);
+		assertThat(bf.getBean(TestBean.class).getName(), equalTo("bar"));
+	}
+
 	@SuppressWarnings("serial")
 	private void localPropertiesOverride(boolean override) {
 		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
@@ -160,4 +218,40 @@ public class PropertySourcesPlaceholderConfigurerTests {
 		}
 	}
 
+	@Test
+	public void customPlaceholderPrefixAndSuffix() {
+		PropertySourcesPlaceholderConfigurer ppc = new PropertySourcesPlaceholderConfigurer();
+		ppc.setPlaceholderPrefix("@<");
+		ppc.setPlaceholderSuffix(">");
+
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.registerBeanDefinition("testBean",
+				rootBeanDefinition(TestBean.class)
+				.addPropertyValue("name", "@<key1>")
+				.addPropertyValue("sex", "${key2}")
+				.getBeanDefinition());
+
+		System.setProperty("key1", "systemKey1Value");
+		System.setProperty("key2", "systemKey2Value");
+		ppc.setEnvironment(new DefaultEnvironment());
+		ppc.postProcessBeanFactory(bf);
+		System.clearProperty("key1");
+		System.clearProperty("key2");
+
+		assertThat(bf.getBean(TestBean.class).getName(), is("systemKey1Value"));
+		assertThat(bf.getBean(TestBean.class).getSex(), is("${key2}"));
+	}
+
+	@Test
+	public void nullValueIsPreserved() {
+		PropertySourcesPlaceholderConfigurer ppc = new PropertySourcesPlaceholderConfigurer();
+		ppc.setNullValue("customNull");
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.registerBeanDefinition("testBean", rootBeanDefinition(TestBean.class)
+				.addPropertyValue("name", "${my.name}")
+				.getBeanDefinition());
+		ppc.setEnvironment(new MockEnvironment().withProperty("my.name", "customNull"));
+		ppc.postProcessBeanFactory(bf);
+		assertThat(bf.getBean(TestBean.class).getName(), nullValue());
+	}
 }