Fix URLDecodeProcessor random test failure (#5328) (#5340)

The randomly-generated input for this test may contain non-URL-safe
characters (such as `%`) so it needs to be URL encoded as well.

Signed-off-by: Andrew Ross <andrross@amazon.com>

Signed-off-by: Andrew Ross <andrross@amazon.com>
(cherry picked from commit 152f3f4)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Signed-off-by: Andrew Ross <andrross@amazon.com>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

modules/ingest-common/src/main/java/org/opensearch/ingest/common/URLDecodeProcessor.java

@@ -32,8 +32,8 @@
 
 package org.opensearch.ingest.common;
 
-import java.io.UnsupportedEncodingException;
 import java.net.URLDecoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Map;
 
 /**
@@ -48,11 +48,7 @@ public final class URLDecodeProcessor extends AbstractStringProcessor<String> {
     }
 
     public static String apply(String value) {
-        try {
-            return URLDecoder.decode(value, "UTF-8");
-        } catch (UnsupportedEncodingException e) {
-            throw new IllegalArgumentException("Could not URL-decode value.", e);
-        }
+        return URLDecoder.decode(value, StandardCharsets.UTF_8);
     }
 
     @Override

modules/ingest-common/src/test/java/org/opensearch/ingest/common/URLDecodeProcessorTests.java

@@ -32,13 +32,14 @@
 
 package org.opensearch.ingest.common;
 
-import java.io.UnsupportedEncodingException;
 import java.net.URLDecoder;
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 
 public class URLDecodeProcessorTests extends AbstractStringProcessorTestCase<String> {
     @Override
     protected String modifyInput(String input) {
-        return "Hello%20G%C3%BCnter" + input;
+        return "Hello%20G%C3%BCnter" + urlEncode(input);
     }
 
     @Override
@@ -48,10 +49,10 @@ protected AbstractStringProcessor<String> newProcessor(String field, boolean ign
 
     @Override
     protected String expectedResult(String input) {
-        try {
-            return "Hello Günter" + URLDecoder.decode(input, "UTF-8");
-        } catch (UnsupportedEncodingException e) {
-            throw new IllegalArgumentException("invalid");
-        }
+        return "Hello Günter" + URLDecoder.decode(urlEncode(input), StandardCharsets.UTF_8);
+    }
+
+    private static String urlEncode(String s) {
+        return URLEncoder.encode(s, StandardCharsets.UTF_8);
     }
 }