Add empty location check to ResourceHttpRequestHandler

ResourceHttpRequestHandler now implements InitializingBean and
checks for empty locations.

Issue: SPR-9186

Author: rstoyanchev

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandler.java

@@ -25,6 +25,7 @@
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
 import org.springframework.http.MediaType;
@@ -38,7 +39,7 @@
 import org.springframework.web.servlet.support.WebContentGenerator;
 
 /**
- * {@link HttpRequestHandler} that serves static resources optimized for superior browser performance 
+ * {@link HttpRequestHandler} that serves static resources optimized for superior browser performance
  * (according to the guidelines of Page Speed, YSlow, etc.) by allowing for flexible cache settings
  * ({@linkplain #setCacheSeconds "cacheSeconds" property}, last-modified support).
  *
@@ -50,7 +51,7 @@
  * (if present) so that a {@code 304} status code will be returned as appropriate, avoiding unnecessary
  * overhead for resources that are already cached by the client. The use of {@code Resource} locations
  * allows resource requests to easily be mapped to locations other than the web application root. For
- * example, resources could be served from a classpath location such as "classpath:/META-INF/public-web-resources/", 
+ * example, resources could be served from a classpath location such as "classpath:/META-INF/public-web-resources/",
  * allowing convenient packaging and serving of resources such as a JavaScript library from within jar files.
  *
  * <p>To ensure that users with a primed browser cache get the latest changes to application-specific
@@ -66,7 +67,7 @@
  * @author Juergen Hoeller
  * @since 3.0.4
  */
-public class ResourceHttpRequestHandler extends WebContentGenerator implements HttpRequestHandler {
+public class ResourceHttpRequestHandler extends WebContentGenerator implements HttpRequestHandler, InitializingBean {
 
 	private static final boolean jafPresent =
 			ClassUtils.isPresent("javax.activation.FileTypeMap", ResourceHttpRequestHandler.class.getClassLoader());
@@ -87,6 +88,9 @@ public void setLocations(List<Resource> locations) {
 		this.locations = locations;
 	}
 
+	public void afterPropertiesSet() throws Exception {
+		Assert.notEmpty(locations, "Locations list must not be empty");
+	}
 
 	/**
 	 * Processes a resource request.

spring-webmvc/src/test/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandlerTests.java

@@ -41,7 +41,7 @@
 public class ResourceHttpRequestHandlerTests {
 
 	private ResourceHttpRequestHandler handler;
-	
+
 	@Before
 	public void setUp() {
 		List<Resource> resourcePaths = new ArrayList<Resource>();
@@ -52,7 +52,7 @@ public void setUp() {
 		handler.setCacheSeconds(3600);
 		handler.setServletContext(new TestServletContext());
 	}
-	
+
 	@Test
 	public void getResource() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
@@ -65,11 +65,11 @@ public void getResource() throws Exception {
 		assertTrue(Long.valueOf(response.getHeader("Expires")) >= System.currentTimeMillis() - 1000 + (3600 * 1000));
 		assertEquals("max-age=3600, must-revalidate", response.getHeader("Cache-Control"));
 		assertTrue(response.containsHeader("Last-Modified"));
-		assertEquals(Long.valueOf(response.getHeader("Last-Modified")).longValue(), 
+		assertEquals(Long.valueOf(response.getHeader("Last-Modified")).longValue(),
 				new ClassPathResource("test/foo.css", getClass()).getFile().lastModified());
 		assertEquals("h1 { color:red; }", response.getContentAsString());
 	}
-	
+
 	@Test
 	public void getResourceWithHtmlMediaType() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
@@ -81,10 +81,10 @@ public void getResourceWithHtmlMediaType() throws Exception {
 		assertTrue(Long.valueOf(response.getHeader("Expires")) >= System.currentTimeMillis() - 1000 + (3600 * 1000));
 		assertEquals("max-age=3600, must-revalidate", response.getHeader("Cache-Control"));
 		assertTrue(response.containsHeader("Last-Modified"));
-		assertEquals(Long.valueOf(response.getHeader("Last-Modified")).longValue(), 
+		assertEquals(Long.valueOf(response.getHeader("Last-Modified")).longValue(),
 				new ClassPathResource("test/foo.html", getClass()).getFile().lastModified());
 	}
-	
+
 	@Test
 	public void getResourceFromAlternatePath() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
@@ -97,11 +97,11 @@ public void getResourceFromAlternatePath() throws Exception {
 		assertTrue(Long.valueOf(response.getHeader("Expires")) >= System.currentTimeMillis() - 1000 + (3600 * 1000));
 		assertEquals("max-age=3600, must-revalidate", response.getHeader("Cache-Control"));
 		assertTrue(response.containsHeader("Last-Modified"));
-		assertEquals(Long.valueOf(response.getHeader("Last-Modified")).longValue(), 
+		assertEquals(Long.valueOf(response.getHeader("Last-Modified")).longValue(),
 				new ClassPathResource("testalternatepath/baz.css", getClass()).getFile().lastModified());
 		assertEquals("h1 { color:red; }", response.getContentAsString());
 	}
-	
+
 	@Test
 	public void getResourceFromSubDirectory() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
@@ -112,7 +112,7 @@ public void getResourceFromSubDirectory() throws Exception {
 		assertEquals("text/javascript", response.getContentType());
 		assertEquals("function foo() { console.log(\"hello world\"); }", response.getContentAsString());
 	}
-	
+
 	@Test
 	public void getResourceFromSubDirectoryOfAlternatePath() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
@@ -138,7 +138,7 @@ public void getResourceViaDirectoryTraversal() throws Exception {
 		response = new MockHttpServletResponse();
 		handler.handleRequest(request, response);
 		assertEquals(404, response.getStatus());
-		
+
 		handler.setLocations(Arrays.<Resource>asList(new ClassPathResource("testsecret/", getClass())));
 		request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, "secret.txt");
 		response = new MockHttpServletResponse();
@@ -158,7 +158,7 @@ public void notModified() throws Exception {
 		handler.handleRequest(request, response);
 		assertEquals(HttpServletResponse.SC_NOT_MODIFIED, response.getStatus());
 	}
-	
+
 	@Test
 	public void modified() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
@@ -169,9 +169,9 @@ public void modified() throws Exception {
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		handler.handleRequest(request, response);
 		assertEquals(HttpServletResponse.SC_OK, response.getStatus());
-		assertEquals("h1 { color:red; }", response.getContentAsString());		
+		assertEquals("h1 { color:red; }", response.getContentAsString());
 	}
-	
+
 	@Test
 	public void directory() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
@@ -191,15 +191,15 @@ public void missingResourcePath() throws Exception {
 		handler.handleRequest(request, response);
 		assertEquals(404, response.getStatus());
 	}
-	
+
 	@Test(expected=IllegalStateException.class)
 	public void noPathWithinHandlerMappingAttribute() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
 		request.setMethod("GET");
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		handler.handleRequest(request, response);
 	}
-	
+
 	@Test(expected=HttpRequestMethodNotSupportedException.class)
 	public void unsupportedHttpMethod() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
@@ -208,7 +208,7 @@ public void unsupportedHttpMethod() throws Exception {
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		handler.handleRequest(request, response);
 	}
-	
+
 	@Test
 	public void resourceNotFound() throws Exception {
 		MockHttpServletRequest request = new MockHttpServletRequest();
@@ -219,6 +219,11 @@ public void resourceNotFound() throws Exception {
 		assertEquals(404, response.getStatus());
 	}
 
+	@Test(expected=IllegalArgumentException.class)
+	public void locationsNotSet() throws Exception {
+		new ResourceHttpRequestHandler().afterPropertiesSet();
+	}
+
 
 	private static class TestServletContext extends MockServletContext {