juneau-doc/docs/Topics/07.juneau-rest-server/06.RestMethod/11.MethodReturnTypes.html

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Method Return Types

<p>
	The return type can be any serializable POJO as defined in {@doc PojoCategories}.
	It can also be <jk>void</jk> if the method is not sending any output (e.g. a request redirect) or is 
	setting the output using the {@link oajr.RestResponse#setOutput(Object)} method.
</p>
<h5 class='figure'>Example:</h5>
<p class='bpcode w800'>
	<ja>@RestMethod</ja>(name=<jsf>GET</jsf>)
	<jk>public</jk> String doGet() {
		<jk>return</jk> <js>"Hello World!"</js>;
	}
</p>
<p>
	Out-of-the-box, besides POJOs, the following return types are handled as special cases:
</p>
<ul class='spaced-list'>
	<li class='jc'>{@link java.io.InputStream}
		<br>The contents are simply piped to the output stream returned by 
		{@link oajr.RestResponse#getNegotiatedOutputStream()}.
		<br>Note that you should call {@link oajr.RestResponse#setContentType(String)} to set 
		the <l>Content-Type</l> header if you use this object type.
	<li class='jc'>{@link java.io.Reader}
		<br>The contents are simply piped to the output stream returned by 
		{@link oajr.RestResponse#getNegotiatedWriter()}.
		<br>Note that you should call {@link oajr.RestResponse#setContentType(String)} to set 
		the <l>Content-Type</l> header if you use this object type.
	<li class='jc'>{@link oaj.Streamable}
		<br>Interface that identifies that an object can be serialized directly to an output stream.
	<li class='jc'>{@link oaj.Writable}
		<br>Interface that identifies that an object can be serialized directly to a writer.
	<li class='jc'>{@link oaj.utils.ZipFileList}
		<br>Special interface for sending zip files as responses.
</ul>
<p>
	This is controlled through the following extensible API:
</p>
<ul class='javatree'>
	<li class='jic'>{@link oajr.ResponseHandler}
	<ul>
		<li class='jc'>{@link oajr.reshandlers.DefaultHandler}
		<li class='jc'>{@link oajr.reshandlers.InputStreamHandler}
		<li class='jc'>{@link oajr.reshandlers.ReaderHandler}
	</ul>
</ul>
<p>
	REST Java methods can generate output in any of the following ways:
</p>
<ul class='spaced-list'>
	<li>
		By returning a serializable POJO, or any of the following:
		<br>{@link java.io.Reader}, {@link java.io.InputStream}, {@link oaj.Streamable}, 
		{@link oaj.Writable} 
	<li>
		By calling {@link oajr.RestResponse#setOutput(Object)} with any of the types above.
	<li>
		By accessing the {@link java.io.Writer} directly by calling 
		{@link oajr.RestResponse#getNegotiatedWriter()} and writing the output yourself.
</ul>
<h5 class='figure'>Example:</h5>
<p class='bpcode w800'>
	<jc>// Equivalent method 1</jc>
	<ja>@RestMethod</ja>(name=<jsf>GET</jsf>, path=<js>"/example1/{personId}"</js>)
	<jk>public</jk> Person doGet1(<ja>@Path</ja>(<js>"personId"</js>) UUID personId) {
		Person p = getPersonById(personId);
		<jk>return</jk> p;
	}

	<jc>// Equivalent method 2</jc>
	<ja>@RestMethod</ja>(name=<jsf>GET</jsf>, path=<js>"/example2/{personId}"</js>)
	<jk>public void</jk> doGet2(RestResponse res, <ja>@Path</ja>(<js>"personId"</js>) UUID personId) {
		Person p = getPersonById(personId);
		res.setOutput(p);
	}

	<jc>// (Sorta) Equivalent method 3</jc>
	<jc>// (Ignores any converters or method-level properties)</jc>
	<ja>@RestMethod</ja>(name=<jsf>GET</jsf>, path=<js>"/example3/{personId}"</js>)
	<jk>public void</jk> doGet3(RestRequest req, RestResponse res, <ja>@Path</ja>(<js>"personId"</js>) UUID personId) {
		Person p = getPersonById(personId);
		String accept = req.getHeader(<js>"Accept"</js>, <js>"text/json"</js>);
		WriterSerializer s = res.getSerializerGroup().getWriterSerializer(accept);
		res.setContentType(s.getResponseContentType());
		s.serialize(p, res.getNegotiatedWriter());
	}
</p>
<ul class='seealso'>
	<li class='jf'>{@link oajr.RestContext#REST_responseHandlers} - For configuring custom response handlers.
</ul>