Fix #12578 pretty print getParameterMap

jetty-core/jetty-util/src/main/java/org/eclipse/jetty/util/Fields.java

@@ -329,7 +329,14 @@ public Iterator<Field> iterator()
      */
     public Map<String, String[]> toStringArrayMap()
     {
-        Map<String, String[]> result = new LinkedHashMap<>();
+        Map<String, String[]> result = new LinkedHashMap<>()
+        {
+            @Override
+            public String toString()
+            {
+                return TypeUtil.toString(this);
+            }
+        };
         fields.forEach((k, f) -> result.put(f.getName(), f.getValues().toArray(new String[0])));
         return result;
     }

jetty-core/jetty-util/src/main/java/org/eclipse/jetty/util/MultiMap.java

@@ -15,7 +15,6 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -330,33 +329,7 @@ public boolean containsSimpleValue(V value)
     @Override
     public String toString()
     {
-        Iterator<Map.Entry<String, List<V>>> iter = entrySet().iterator();
-        StringBuilder sb = new StringBuilder();
-        sb.append('{');
-        boolean delim = false;
-        while (iter.hasNext())
-        {
-            Map.Entry<String, List<V>> e = iter.next();
-            if (delim)
-            {
-                sb.append(", ");
-            }
-            String key = e.getKey();
-            List<V> vals = e.getValue();
-            sb.append(key);
-            sb.append('=');
-            if (vals.size() == 1)
-            {
-                sb.append(vals.get(0));
-            }
-            else
-            {
-                sb.append(vals);
-            }
-            delim = true;
-        }
-        sb.append('}');
-        return sb.toString();
+        return TypeUtil.toString(this);
     }
 
     /**

jetty-core/jetty-util/src/main/java/org/eclipse/jetty/util/TypeUtil.java

@@ -35,6 +35,7 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.ListIterator;
+import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.ServiceConfigurationError;
@@ -864,4 +865,39 @@ public static boolean isDeclaredMethodOn(Object object, String methodName, Class
             return false;
         }
     }
+
+    /**
+     * Pretty print a map. Specifically expanding Array values.
+     * @param map The map to render as a String
+     * @return A String representation of the map
+     */
+    public static String toString(Map<?, ?> map)
+    {
+        if (map.isEmpty())
+            return "{}";
+
+        StringBuilder sb = new StringBuilder();
+        sb.append('{');
+        for (Iterator<? extends Map.Entry<?, ?>> i = map.entrySet().iterator(); i.hasNext();)
+        {
+            Map.Entry<?, ?> e = i.next();
+            Object key = e.getKey();
+            sb.append(key);
+            sb.append('=');
+
+            Object value = e.getValue();
+
+            if (value == null)
+                sb.append("null");
+            else if (value.getClass().isArray())
+                sb.append(Arrays.asList((Object[])value));
+            else
+                sb.append(value);
+            if (i.hasNext())
+                sb.append(',');
+        }
+        sb.append('}');
+        return sb.toString();
+    }
+
 }

jetty-core/jetty-util/src/test/java/org/eclipse/jetty/util/MultiMapTest.java

@@ -462,12 +462,12 @@ public void testToString()
         MultiMap<String> mm = new MultiMap<>();
         mm.put("color", "red");
 
-        assertEquals("{color=red}", mm.toString());
+        assertEquals("{color=[red]}", mm.toString());
 
         mm.putValues("food", "apple", "cherry", "raspberry");
 
-        String expected1 = "{color=red, food=[apple, cherry, raspberry]}";
-        String expected2 = "{food=[apple, cherry, raspberry], color=red}";
+        String expected1 = "{color=[red],food=[apple, cherry, raspberry]}";
+        String expected2 = "{food=[apple, cherry, raspberry],color=[red]}";
         String actual = mm.toString();
         assertTrue(actual.equals(expected1) || actual.equals(expected2));
     }

jetty-ee10/jetty-ee10-servlet/src/test/java/org/eclipse/jetty/ee10/servlet/RequestTest.java

@@ -16,6 +16,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.io.PrintWriter;
 import java.io.UnsupportedEncodingException;
 import java.net.InetAddress;
 import java.net.Socket;
@@ -626,4 +627,49 @@ protected void service(HttpServletRequest request, HttpServletResponse resp) thr
             assertThat(date, containsString(":"));
         }
     }
+
+    @Test
+    public void testParameters() throws Exception
+    {
+        final AtomicReference<String> parameterMap = new AtomicReference<>();
+
+        startServer(new HttpServlet()
+        {
+            @Override
+            protected void service(HttpServletRequest request, HttpServletResponse resp) throws IOException
+            {
+                parameterMap.set(request.getParameterMap().toString());
+                PrintWriter out = resp.getWriter();
+                out.println(request.getParameter("a"));
+                out.println(request.getParameterValues("a")[1]);
+                out.println(request.getParameterValues("a")[2]);
+                out.println(Arrays.asList(request.getParameterValues("b")));
+                out.println(Arrays.asList(request.getParameterValues("c")));
+                out.println(Arrays.asList(request.getParameterValues("d")));
+
+            }
+        });
+
+        String rawResponse = _connector.getResponse(
+            """
+                POST /test/parameters?a=1&a=2&b=one&c= HTTP/1.1\r
+                Host: localhost\r
+                Connection: close\r
+                Content-Type: application/x-www-form-urlencoded\r
+                Content-Length: 23\r
+                \r
+                a=3&b=two&b=three&d=xyz\r
+                """);
+        HttpTester.Response response = HttpTester.parseResponse(rawResponse);
+        assertThat(response.getStatus(), is(HttpStatus.OK_200));
+        assertThat(parameterMap.get(), is("{a=[1, 2, 3],b=[one, two, three],c=[],d=[xyz]}"));
+        assertThat(response.getContent().replaceAll("\r\n", "\n"), is("""
+            1
+            2
+            3
+            [one, two, three]
+            []
+            [xyz]
+            """));
+    }
 }