src/main/java/js/http/encoder/ServerEncoders.java
@Override
	public ValueWriter getValueWriter(ContentType contentType) {
		ValueWriter writer = writers.get(contentType);
		if (writer == null) {
			throw new BugError("No return value writer for content type |%s|.", contentType);
		}
		return writer;
	}
@Override
	public ValueWriter getValueWriter(ContentType contentType) {
		ValueWriter writer = writers.get(contentType);
		if (writer == null) {
			throw new BugError("No return value writer for content type |%s|.", contentType);
		}
		return writer;
	}
Get return value writer able to handle requested content type. Content type argument should identify a registered value
writer. If no writer found throws bug error.
<p>
Recommend way to use this method is to provide content type instance returned by {@link #getContentTypeForValue(Object)}.

<pre>
Object value = ...
ContentType contentType = encoders.getContentTypeForValue(value);
ValueWriter writer = encoders.getValueWriter(contentType);
...
</pre>

@param contentType content type for return value.
@return return value writer, never null.
@throws BugError if no value writer registered for requested content type.