adding a convenience class to handle query parameters in response to HUDSON-8056.

core/src/main/java/hudson/util/QueryParameterMap.java

+/*
+ * The MIT License
+ *
+ * Copyright (c) 2011, CloudBees, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package hudson.util;
+
+import javax.servlet.http.HttpServletRequest;
+import java.io.UnsupportedEncodingException;
+import java.net.URLDecoder;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Parses the query string of the URL into a key/value pair.
+ *
+ * <p>
+ * This class is even useful on the server side, as {@link HttpServletRequest#getParameter(String)}
+ * can try to parse into the payload (and that can cause an exception if the payload is already consumed.
+ * See HUDSON-8056.)
+ *
+ * <p>
+ * So if you are handling the payload yourself and only want to access the query parameters,
+ * use this class.
+ *
+ * @author Kohsuke Kawaguchi
+ * @since 1.394
+ */
+public class QueryParameterMap {
+    private final Map<String,List<String>> store = new HashMap<String, List<String>>();
+
+    /**
+     * @param queryString
+     *      String that looks like "abc=def&ghi=jkl"
+     */
+    public QueryParameterMap(String queryString) {
+        if (queryString==null || queryString.length()==0)   return;
+        try {
+            for (String param : queryString.split("&")) {
+                String[] kv = param.split("=");
+                String key = URLDecoder.decode(kv[0], "UTF-8");
+                String value = URLDecoder.decode(kv[1], "UTF-8");
+                List<String> values = store.get(key);
+                if (values == null)
+                    store.put(key, values = new ArrayList<String>());
+                values.add(value);
+            }
+        } catch (UnsupportedEncodingException e) {
+            throw new AssertionError(e);
+        }
+    }
+
+    public QueryParameterMap(HttpServletRequest req) {
+        this(req.getQueryString());
+    }
+
+    public String get(String name) {
+        List<String> v = store.get(name);
+        return v!=null?v.get(0):null;
+    }
+
+    public List<String> getAll(String name) {
+        List<String> v = store.get(name);
+        return v!=null? Collections.unmodifiableList(v) : Collections.<String>emptyList();
+    }
+}