HttpURLConnection Invalid HTTP method: PATCH

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");

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.

There is a Won't Fix bug in OpenJDK for this: https://bugs.openjdk.java.net/browse/JDK-7016595

However, with Apache Http-Components Client 4.2+ this is possible. It has a custom networking implementation, thus using all standard HTTP methods like PATCH is possible. It even has a HttpPatch class supporting the patch method.

CloseableHttpClient httpClient = HttpClients.createDefault();HttpPatch httpPatch = new HttpPatch(new URI("http://example.com"));CloseableHttpResponse response = httpClient.execute(httpPatch);

Maven Coordinates:

<dependency>    <groupId>org.apache.httpcomponents</groupId>    <artifactId>httpclient</artifactId>    <version>4.2+</version></dependency>