HttpURLConnection Invalid HTTP method: PATCH

Question

When I try to use a non-standard HTTP Method like PATCH with URLConnection:

    HttpURLConnection conn = (HttpURLConnection) new URL("http://example.com").openConnection();     conn.setRequestMethod("PATCH"); 

I get an exception:

java.net.ProtocolException: Invalid HTTP method: PATCH at java.net.HttpURLConnection.setRequestMethod(HttpURLConnection.java:440) 

Using a higher level API like Jersey generates the same error. Is there a workaround to issue a PATCH HTTP request?

Answer 1

There are a lot of good answers, so here is mine (not work in jdk12):

import java.io.IOException; import java.lang.reflect.Field; import java.lang.reflect.Modifier; import java.net.HttpURLConnection; import java.net.URL; import java.util.Arrays; import java.util.LinkedHashSet; import java.util.Set;  public class SupportPatch {     public static void main(String... args) throws IOException {         allowMethods("PATCH");          HttpURLConnection conn = (HttpURLConnection) new URL("http://example.com").openConnection();         conn.setRequestMethod("PATCH");     }      private static void allowMethods(String... methods) {         try {             Field methodsField = HttpURLConnection.class.getDeclaredField("methods");              Field modifiersField = Field.class.getDeclaredField("modifiers");             modifiersField.setAccessible(true);             modifiersField.setInt(methodsField, methodsField.getModifiers() & ~Modifier.FINAL);              methodsField.setAccessible(true);              String[] oldMethods = (String[]) methodsField.get(null);             Set<String> methodsSet = new LinkedHashSet<>(Arrays.asList(oldMethods));             methodsSet.addAll(Arrays.asList(methods));             String[] newMethods = methodsSet.toArray(new String[0]);              methodsField.set(null/*static field*/, newMethods);         } catch (NoSuchFieldException | IllegalAccessException e) {             throw new IllegalStateException(e);         }     } } 

It also uses reflection, but instead of hacking into every connection object we're hacking HttpURLConnection#methods static field which is used in the checks internally.

Answer 2

Yes there is workaround for this. Use

X-HTTP-Method-Override

. This header can be used in a POST request to “fake” other HTTP methods. Simply set the value of the X-HTTP-Method-Override header to the HTTP method you would like to actually perform. So use following code.

conn.setRequestProperty("X-HTTP-Method-Override", "PATCH"); conn.setRequestMethod("POST");