[SPR-6025] PropertyPlaceholderUtils introduced

Author: Rob Harrop

org.springframework.core/src/main/java/org/springframework/util/PropertyPlaceholderUtils.java

@@ -0,0 +1,106 @@
+/*
+ * Copyright 2002-2009 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.util;
+
+import java.util.Properties;
+
+/**
+ * Utility class for working with Strings that have placeholder values in them. A placeholder takes the form
+ * <code>${name}</code>. Using <code>PropertyPlaceholderUtils</code> these placeholders can be substituted for
+ * user-supplied values. <p> Values for substitution can be supplied using a {@link Properties} instance or using a
+ * {@link PlaceholderResolver}.
+ *
+ * @author Juergen Hoeller
+ * @author Rob Harrop
+ * @since 3.0
+ */
+public class PropertyPlaceholderUtils {
+
+	/** Prefix for property placeholders: "${" */
+	public static final String PLACEHOLDER_PREFIX = "${";
+
+	/** Suffix for property placeholders: "}" */
+	public static final String PLACEHOLDER_SUFFIX = "}";
+
+	/**
+	 * Replaces all placeholders of format <code>${name}</code> with the corresponding property from the supplied {@link
+	 * Properties}.
+	 *
+	 * @param value the value containing the placeholders to be replaced.
+	 * @param properties the <code>Properties</code> to use for replacement.
+	 * @return the supplied value with placeholders replaced inline.
+	 */
+	public static String replacePlaceholders(String value, final Properties properties) {
+		Assert.notNull(properties, "Argument 'properties' must not be null.");
+		return replacePlaceholders(value, new PlaceholderResolver() {
+
+			public String resolvePlaceholder(String placeholderName) {
+				return properties.getProperty(placeholderName);
+			}
+		});
+	}
+
+	/**
+	 * Replaces all placeholders of format <code>${name}</code> with the value returned from the supplied {@link
+	 * PlaceholderResolver}.
+	 *
+	 * @param value the value containing the placeholders to be replaced.
+	 * @param placeholderResolver the <code>PlaceholderResolver</code> to use for replacement.
+	 * @return the supplied value with placeholders replaced inline.
+	 */
+	public static String replacePlaceholders(String value, PlaceholderResolver placeholderResolver) {
+		StringBuilder result = new StringBuilder(value);
+
+		int startIndex = result.indexOf(PLACEHOLDER_PREFIX);
+		while (startIndex != -1) {
+			int endIndex = result.indexOf(PLACEHOLDER_SUFFIX, startIndex + PLACEHOLDER_PREFIX.length());
+			if (endIndex != -1) {
+				String placeholder = result.substring(startIndex + PLACEHOLDER_PREFIX.length(), endIndex);
+				int nextIndex = endIndex + PLACEHOLDER_SUFFIX.length();
+
+				String propVal = placeholderResolver.resolvePlaceholder(placeholder);
+				if (propVal != null) {
+					result.replace(startIndex, endIndex + PLACEHOLDER_SUFFIX.length(), propVal);
+					nextIndex = startIndex + propVal.length();
+				}
+
+				startIndex = result.indexOf(PLACEHOLDER_PREFIX, nextIndex);
+			}
+			else {
+				startIndex = -1;
+			}
+		}
+
+		return result.toString();
+	}
+
+	/**
+	 * Strategy interface used to resolve replacement values for placeholders contained in Strings.
+	 *
+	 * @see org.springframework.util.PropertyPlaceholderUtils
+	 */
+	public static interface PlaceholderResolver {
+
+		/**
+		 * Resolves the supplied placeholder name into the replacement value.
+		 *
+		 * @param placeholderName the name of the placeholder to resolve.
+		 * @return the replacement value or <code>null</code> if no replacement is to be made.
+		 */
+		String resolvePlaceholder(String placeholderName);
+	}
+}

org.springframework.core/src/test/java/org/springframework/util/PropertyPlaceholderUtilsTests.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2002-2009 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.util;
+
+import java.util.Properties;
+
+import org.junit.Test;
+import static org.junit.Assert.assertEquals;
+
+/** @author Rob Harrop */
+public class PropertyPlaceholderUtilsTests {
+
+	@Test
+	public void testWithProperties() {
+		String text = "foo=${foo}";
+		Properties props = new Properties();
+		props.setProperty("foo", "bar");
+
+		assertEquals("foo=bar", PropertyPlaceholderUtils.replacePlaceholders(text, props));
+	}
+
+	@Test
+	public void testWithMultipleProperties() {
+		String text = "foo=${foo},bar=${bar}";
+		Properties props = new Properties();
+		props.setProperty("foo", "bar");
+		props.setProperty("bar", "baz");
+
+		assertEquals("foo=bar,bar=baz", PropertyPlaceholderUtils.replacePlaceholders(text, props));
+	}
+
+	@Test
+	public void testWithResolver() {
+		String text = "foo=${foo}";
+
+		assertEquals("foo=bar",
+				PropertyPlaceholderUtils.replacePlaceholders(text, new PropertyPlaceholderUtils.PlaceholderResolver() {
+
+					public String resolvePlaceholder(String placeholderName) {
+						if ("foo".equals(placeholderName)) {
+							return "bar";
+						}
+						else {
+							return null;
+						}
+					}
+				}));
+	}
+
+	@Test
+	public void testUnresolvedPlaceholderIsIgnored() {
+		String text = "foo=${foo},bar=${bar}";
+		Properties props = new Properties();
+		props.setProperty("foo", "bar");
+		
+		assertEquals("foo=bar,bar=${bar}", PropertyPlaceholderUtils.replacePlaceholders(text, props));
+	}
+}