Servlet 3 multipart request implements getParameterNames defensively (for WebLogic 12 compatibility)

This commit also includes lazy resolution support for StandardServletMultipartResolver, along the lines of existing lazy mode in CommonsMultipartResolver.

Issue: SPR-11074
Issue: SPR-11730
(cherry picked from commit 82336c3)

Author: jhoeller

spring-web/src/main/java/org/springframework/web/multipart/support/DefaultMultipartHttpServletRequest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -19,7 +19,7 @@
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.HashMap;
-import java.util.HashSet;
+import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;
 import javax.servlet.http.HttpServletRequest;
@@ -33,6 +33,8 @@
  * {@link org.springframework.web.multipart.MultipartHttpServletRequest}
  * interface. Provides management of pre-generated parameter values.
  *
+ * <p>Used by {@link org.springframework.web.multipart.commons.CommonsMultipartResolver}.
+ *
  * @author Trevor D. Cook
  * @author Juergen Hoeller
  * @author Arjen Poutsma
@@ -75,12 +77,17 @@ public DefaultMultipartHttpServletRequest(HttpServletRequest request) {
 
 	@Override
 	public Enumeration<String> getParameterNames() {
-		Set<String> paramNames = new HashSet<String>();
+		Map<String, String[]> multipartParameters = getMultipartParameters();
+		if (multipartParameters.isEmpty()) {
+			return super.getParameterNames();
+		}
+
+		Set<String> paramNames = new LinkedHashSet<String>();
 		Enumeration<String> paramEnum = super.getParameterNames();
 		while (paramEnum.hasMoreElements()) {
 			paramNames.add(paramEnum.nextElement());
 		}
-		paramNames.addAll(getMultipartParameters().keySet());
+		paramNames.addAll(multipartParameters.keySet());
 		return Collections.enumeration(paramNames);
 	}
 

spring-web/src/main/java/org/springframework/web/multipart/support/StandardMultipartHttpServletRequest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -21,6 +21,10 @@
 import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
+import java.util.Enumeration;
+import java.util.LinkedHashSet;
+import java.util.Set;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.Part;
 
@@ -45,22 +49,47 @@ public class StandardMultipartHttpServletRequest extends AbstractMultipartHttpSe
 
 	private static final String FILENAME_KEY = "filename=";
 
+	private Set<String> multipartParameterNames;
+
 
 	/**
-	 * Create a new StandardMultipartHttpServletRequest wrapper for the given request.
+	 * Create a new StandardMultipartHttpServletRequest wrapper for the given request,
+	 * immediately parsing the multipart content.
 	 * @param request the servlet request to wrap
 	 * @throws MultipartException if parsing failed
 	 */
 	public StandardMultipartHttpServletRequest(HttpServletRequest request) throws MultipartException {
+		this(request, false);
+	}
+
+	/**
+	 * Create a new StandardMultipartHttpServletRequest wrapper for the given request.
+	 * @param request the servlet request to wrap
+	 * @param lazyParsing whether multipart parsing should be triggered lazily on
+	 * first access of multipart files or parameters
+	 * @throws MultipartException if an immediate parsing attempt failed
+	 */
+	public StandardMultipartHttpServletRequest(HttpServletRequest request, boolean lazyParsing) throws MultipartException {
 		super(request);
+		if (!lazyParsing) {
+			parseRequest(request);
+		}
+	}
+
+
+	private void parseRequest(HttpServletRequest request) {
 		try {
 			Collection<Part> parts = request.getParts();
+			this.multipartParameterNames = new LinkedHashSet<String>(parts.size());
 			MultiValueMap<String, MultipartFile> files = new LinkedMultiValueMap<String, MultipartFile>(parts.size());
 			for (Part part : parts) {
 				String filename = extractFilename(part.getHeader(CONTENT_DISPOSITION));
 				if (filename != null) {
 					files.add(part.getName(), new StandardMultipartFile(part, filename));
 				}
+				else {
+					this.multipartParameterNames.add(part.getName());
+				}
 			}
 			setMultipartFiles(files);
 		}
@@ -95,6 +124,29 @@ private String extractFilename(String contentDisposition) {
 	}
 
 
+	@Override
+	protected void initializeMultipart() {
+		parseRequest(getRequest());
+	}
+
+	@Override
+	public Enumeration<String> getParameterNames() {
+		if (this.multipartParameterNames == null) {
+			initializeMultipart();
+		}
+		if (this.multipartParameterNames.isEmpty()) {
+			return super.getParameterNames();
+		}
+
+		Set<String> paramNames = new LinkedHashSet<String>();
+		Enumeration<String> paramEnum = super.getParameterNames();
+		while (paramEnum.hasMoreElements()) {
+			paramNames.add(paramEnum.nextElement());
+		}
+		paramNames.addAll(this.multipartParameterNames);
+		return Collections.enumeration(paramNames);
+	}
+
 	@Override
 	public String getMultipartContentType(String paramOrFileName) {
 		try {

spring-web/src/main/java/org/springframework/web/multipart/support/StandardServletMultipartResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -45,6 +45,22 @@
  */
 public class StandardServletMultipartResolver implements MultipartResolver {
 
+	private boolean resolveLazily = false;
+
+
+	/**
+	 * Set whether to resolve the multipart request lazily at the time of
+	 * file or parameter access.
+	 * <p>Default is "false", resolving the multipart elements immediately, throwing
+	 * corresponding exceptions at the time of the {@link #resolveMultipart} call.
+	 * Switch this to "true" for lazy multipart parsing, throwing parse exceptions
+	 * once the application attempts to obtain multipart files or parameters.
+	 */
+	public void setResolveLazily(boolean resolveLazily) {
+		this.resolveLazily = resolveLazily;
+	}
+
+
 	@Override
 	public boolean isMultipart(HttpServletRequest request) {
 		// Same check as in Commons FileUpload...
@@ -57,7 +73,7 @@ public boolean isMultipart(HttpServletRequest request) {
 
 	@Override
 	public MultipartHttpServletRequest resolveMultipart(HttpServletRequest request) throws MultipartException {
-		return new StandardMultipartHttpServletRequest(request);
+		return new StandardMultipartHttpServletRequest(request, this.resolveLazily);
 	}
 
 	@Override