Add "POST /render" endpoint to picoweb server.

It expects a JSON body like
  { "source": PLANTUML_SOURCE_STRING, "options": ARRAY_OF_STRINGS }

And returns the rendered diagram with suitable Content-Type header (all output formats are supported).

src/net/sourceforge/plantuml/FileFormat.java

@@ -60,8 +60,37 @@ import net.sourceforge.plantuml.ugraphic.UFont;
  * 
  */
 public enum FileFormat {
-	PNG, SVG, EPS, EPS_TEXT, ATXT, UTXT, XMI_STANDARD, XMI_STAR, XMI_ARGO, SCXML, PDF, MJPEG, ANIMATED_GIF, HTML, HTML5,
-	VDX, LATEX, LATEX_NO_PREAMBLE, BASE64, BRAILLE_PNG, PREPROC;
+	PNG("image/png"),
+	SVG("image/svg+xml"),
+	EPS("application/postscript"),
+	EPS_TEXT("application/postscript"),
+	ATXT("text/plain"),
+	UTXT("text/plain;charset=UTF-8"),
+	XMI_STANDARD("application/vnd.xmi+xml"),
+	XMI_STAR("application/vnd.xmi+xml"),
+	XMI_ARGO("application/vnd.xmi+xml"),
+	SCXML("application/scxml+xml"),
+	PDF("application/pdf"),
+	MJPEG("video/x-msvideo"),
+	ANIMATED_GIF("image/gif"),
+	HTML("text/html"),
+	HTML5("text/html"),
+	VDX("application/vnd.visio.xml"),
+	LATEX("application/x-latex"),
+	LATEX_NO_PREAMBLE("application/x-latex"),
+	BASE64("text/plain; charset=x-user-defined"),
+	BRAILLE_PNG("image/png"),
+	PREPROC("text/plain");
+
+	private final String mimeType;
+
+	FileFormat(String mimeType) {
+		this.mimeType = mimeType;
+	}
+
+	public String getMimeType() {
+		return mimeType;
+	}
 
 	/**
 	 * Returns the file format to be used for that format.

src/net/sourceforge/plantuml/SourceStringReader.java

@@ -225,7 +225,7 @@ public class SourceStringReader {
 
 	}
 
-	private void noStartumlFound(OutputStream os, FileFormatOption fileFormatOption, long seed) throws IOException {
+	public ImageData noStartumlFound(OutputStream os, FileFormatOption fileFormatOption, long seed) throws IOException {
 		final TextBlockBackcolored error = GraphicStrings.createForError(Arrays.asList("No @startuml/@enduml found"),
 				fileFormatOption.isUseRedForError());
 		HColor backcolor = error.getBackcolor();
@@ -233,7 +233,7 @@ public class SourceStringReader {
 				null, ClockwiseTopRightBottomLeft.none(), backcolor);
 		final ImageBuilder imageBuilder = ImageBuilder.build(imageParameter);
 		imageBuilder.setUDrawable(error);
-		imageBuilder.writeImageTOBEMOVED(fileFormatOption, seed, os);
+		return imageBuilder.writeImageTOBEMOVED(fileFormatOption, seed, os);
 	}
 
 	public final List<BlockUml> getBlocks() {

src/net/sourceforge/plantuml/picoweb/BadRequest400.java

@@ -0,0 +1,14 @@
+package net.sourceforge.plantuml.picoweb;
+
+import java.io.IOException;
+
+public class BadRequest400 extends IOException {
+
+	public BadRequest400(String message) {
+		super(message);
+	}
+
+	public BadRequest400(String message, Throwable cause) {
+		super(message, cause);
+	}
+}

src/net/sourceforge/plantuml/picoweb/PicoWebServer.java

@@ -36,34 +36,40 @@
  */
 package net.sourceforge.plantuml.picoweb;
 
+import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
-import java.io.BufferedReader;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.InputStreamReader;
 import java.io.OutputStream;
+import java.io.PrintWriter;
 import java.net.InetAddress;
 import java.net.ServerSocket;
 import java.net.Socket;
+import java.util.Collections;
 import java.util.Date;
 import java.util.List;
-import java.util.StringTokenizer;
 
 import net.sourceforge.plantuml.BlockUml;
 import net.sourceforge.plantuml.ErrorUml;
 import net.sourceforge.plantuml.FileFormat;
 import net.sourceforge.plantuml.FileFormatOption;
+import net.sourceforge.plantuml.LineLocationImpl;
+import net.sourceforge.plantuml.Option;
 import net.sourceforge.plantuml.SourceStringReader;
+import net.sourceforge.plantuml.StringLocated;
 import net.sourceforge.plantuml.StringUtils;
-import net.sourceforge.plantuml.code.NoPlantumlCompressionException;
 import net.sourceforge.plantuml.code.Transcoder;
 import net.sourceforge.plantuml.code.TranscoderUtil;
 import net.sourceforge.plantuml.core.Diagram;
 import net.sourceforge.plantuml.core.ImageData;
 import net.sourceforge.plantuml.error.PSystemError;
+import net.sourceforge.plantuml.error.PSystemErrorUtils;
 import net.sourceforge.plantuml.graphic.QuoteUtils;
 import net.sourceforge.plantuml.version.Version;
 
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static net.sourceforge.plantuml.ErrorUmlType.SYNTAX_ERROR;
+
 public class PicoWebServer implements Runnable {
 
 	private final Socket connect;
@@ -80,6 +86,10 @@ public class PicoWebServer implements Runnable {
 		final InetAddress bindAddress1 = bindAddress == null ? null : InetAddress.getByName(bindAddress);
 		final ServerSocket serverConnect = new ServerSocket(port, 50, bindAddress1);
 		System.err.println("webPort=" + serverConnect.getLocalPort());
+		serverLoop(serverConnect);
+	}
+
+	public static void serverLoop(final ServerSocket serverConnect) throws IOException {
 		while (true) {
 			final PicoWebServer myServer = new PicoWebServer(serverConnect.accept());
 			final Thread thread = new Thread(myServer);
@@ -88,30 +98,25 @@ public class PicoWebServer implements Runnable {
 	}
 
 	public void run() {
-		BufferedReader in = null;
+		BufferedInputStream in = null;
 		BufferedOutputStream out = null;
 
 		try {
-			in = new BufferedReader(new InputStreamReader(connect.getInputStream(), "UTF-8"));
+			in = new BufferedInputStream(connect.getInputStream());
 			out = new BufferedOutputStream(connect.getOutputStream());
 
-			final String first = in.readLine();
-			if (first == null) {
+			final ReceivedHTTPRequest request = ReceivedHTTPRequest.fromStream(in);
+			if (request.getMethod().equals("GET")) {
+				if (request.getPath().startsWith("/png/") && handleGET(request, out, FileFormat.PNG))
 					return;
-			}
-
-			final StringTokenizer parse = new StringTokenizer(first);
-			final String method = parse.nextToken().toUpperCase();
-
-			if (method.equals("GET")) {
-				final String path = parse.nextToken();
-				if (path.startsWith("/png/") && sendDiagram(out, path, "image/png", FileFormat.PNG))
+				if (request.getPath().startsWith("/plantuml/png/") && handleGET(request, out, FileFormat.PNG))
 					return;
-				if (path.startsWith("/plantuml/png/") && sendDiagram(out, path, "image/png", FileFormat.PNG))
+				if (request.getPath().startsWith("/svg/") && handleGET(request, out, FileFormat.SVG))
 					return;
-				if (path.startsWith("/svg/") && sendDiagram(out, path, "image/svg+xml", FileFormat.SVG))
+				if (request.getPath().startsWith("/plantuml/svg/") && handleGET(request, out, FileFormat.SVG))
 					return;
-				if (path.startsWith("/plantuml/svg/") && sendDiagram(out, path, "image/svg+xml", FileFormat.SVG))
+			} else if (request.getMethod().equals("POST") && request.getPath().equals("/render")) {
+				handleRenderRequest(request, out);
 				return;
 			}
 			write(out, "HTTP/1.1 302 Found");
@@ -120,7 +125,12 @@ public class PicoWebServer implements Runnable {
 			out.flush();
 
 		} catch (Throwable e) {
+			try {
+				sendError(e, out);
+			}
+			catch (Throwable e1) {
 				e.printStackTrace();
+			}
 		} finally {
 			try {
 				in.close();
@@ -132,26 +142,74 @@ public class PicoWebServer implements Runnable {
 		}
 	}
 
-	private boolean sendDiagram(BufferedOutputStream out, String path, final String mime, final FileFormat format)
-			throws NoPlantumlCompressionException, IOException {
-		final int x = path.lastIndexOf('/');
-		final String compressed = path.substring(x + 1);
+	private boolean handleGET(ReceivedHTTPRequest request, BufferedOutputStream out, final FileFormat format) throws IOException {
+		final int x = request.getPath().lastIndexOf('/');
+		final String compressed = request.getPath().substring(x + 1);
 		final Transcoder transcoder = TranscoderUtil.getDefaultTranscoderProtected();
 		final String source = transcoder.decode(compressed);
 		final SourceStringReader ssr = new SourceStringReader(source);
 
 		final List<BlockUml> blocks = ssr.getBlocks();
 		if (blocks.size() > 0) {
+			final FileFormatOption fileFormatOption = new FileFormatOption(format);
 			final Diagram system = blocks.get(0).getDiagram();
 			final ByteArrayOutputStream os = new ByteArrayOutputStream();
-			final ImageData imageData = system.exportDiagram(os, 0, new FileFormatOption(format));
+			final ImageData imageData = system.exportDiagram(os, 0, fileFormatOption);
 			os.close();
-			final byte[] fileData = os.toByteArray();
-			write(out, "HTTP/1.1 " + httpReturnCode(imageData.getStatus()));
+			sendDiagram(out, system, fileFormatOption, httpReturnCode(imageData.getStatus()), imageData, os.toByteArray());
+			return true;
+		}
+		return false;
+	}
+
+	private void handleRenderRequest(ReceivedHTTPRequest request, BufferedOutputStream out) throws Exception {
+		if (request.getBody().length == 0) {
+			throw new BadRequest400("No request body");
+		}
+
+		final RenderRequest renderRequest;
+		try {
+			renderRequest = RenderRequest.fromJson(new String(request.getBody(), UTF_8));
+		} catch (Exception e) {
+			throw new BadRequest400("Error parsing request json: " + e.getMessage(), e);
+		}
+
+		final Option option = new Option(renderRequest.getOptions());
+
+		final String source = renderRequest.getSource().startsWith("@start")
+				? renderRequest.getSource()
+				: "@startuml\n" + renderRequest.getSource() + "\n@enduml";
+
+		final SourceStringReader ssr = new SourceStringReader(option.getDefaultDefines(), source, option.getConfig());
+		final ByteArrayOutputStream os = new ByteArrayOutputStream();
+		final Diagram system;
+		final ImageData imageData;
+
+		if (ssr.getBlocks().size() == 0) {
+			system = PSystemErrorUtils.buildV2(
+					null,
+					new ErrorUml(SYNTAX_ERROR, "No @startuml/@enduml found", 0, new LineLocationImpl("", null)),
+					null,
+					Collections.<StringLocated>emptyList()
+			);
+			imageData = ssr.noStartumlFound(os, option.getFileFormatOption(),42);
+		} else {
+			system = ssr.getBlocks().get(0).getDiagram();
+			imageData = system.exportDiagram(os, 0, option.getFileFormatOption());
+		}
+
+		sendDiagram(out, system, option.getFileFormatOption(), "200", imageData, os.toByteArray());
+	}
+
+	private void sendDiagram(final BufferedOutputStream out, final Diagram system, final FileFormatOption fileFormatOption,
+							 final String returnCode, final ImageData imageData, final byte[] fileData)
+			throws IOException {
+
+		write(out, "HTTP/1.1 " + returnCode);
 		write(out, "Cache-Control: no-cache");
 		write(out, "Server: PlantUML PicoWebServer " + Version.versionString());
 		write(out, "Date: " + new Date());
-			write(out, "Content-type: " + mime);
+		write(out, "Content-type: " + fileFormatOption.getFileFormat().getMimeType());
 		write(out, "Content-length: " + fileData.length);
 		write(out, "X-PlantUML-Diagram-Width: " + imageData.getWidth());
 		write(out, "X-PlantUML-Diagram-Height: " + imageData.getHeight());
@@ -170,9 +228,25 @@ public class PicoWebServer implements Runnable {
 		out.flush();
 		out.write(fileData);
 		out.flush();
-			return true;
 	}
-		return false;
+
+	private void sendError(Throwable e, BufferedOutputStream out) throws Exception {
+		final ByteArrayOutputStream baos = new ByteArrayOutputStream();
+		final PrintWriter printWriter = new PrintWriter(baos);
+
+		if (e instanceof BadRequest400 && e.getCause() == null) {
+			printWriter.write(e.getMessage());
+		} else {
+			e.printStackTrace(printWriter);
+		}
+		printWriter.close();
+
+		write(out, "HTTP/1.1 " + (e instanceof BadRequest400 ? "400 Bad Request" : "500 Internal Server Error"));
+		write(out, "Content-type: text/plain");
+		write(out, "Content-length: " + baos.size());
+		write(out, "");
+		out.write(baos.toByteArray());
+		out.flush();
 	}
 
 	private String httpReturnCode(int status) {

src/net/sourceforge/plantuml/picoweb/PicoWebServerTest.java

@@ -0,0 +1,316 @@
+package net.sourceforge.plantuml.picoweb;
+
+import net.sourceforge.plantuml.json.Json;
+import net.sourceforge.plantuml.json.JsonObject;
+
+import javax.imageio.ImageIO;
+import javax.imageio.stream.MemoryCacheImageInputStream;
+import java.awt.image.BufferedImage;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.HttpURLConnection;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.net.URL;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static net.sourceforge.plantuml.code.TranscoderUtil.getDefaultTranscoder;
+
+// Newer Java versions have nice built-in HTTP classes in the jdk.incubator.httpclient / java.net.http packages
+// but PlantUML supports older Java versions so the tests here use a kludgy approach to HTTP.
+
+// Multi-line strings here start with a "" so that IDE auto-indenting will leave the rest of the string nicely
+// aligned
+
+public class PicoWebServerTest {
+
+	public static void main(String[] args) throws Exception {
+		startServer();
+		test_basic_http();
+		test_GET_png();
+		test_GET_svg();
+		test_POST_render();
+		test_unknown_path();
+	}
+
+	//
+	// Test Cases
+	//
+
+	private static void test_basic_http() throws Exception {
+		assert httpRaw(
+				""
+		).equals("" +
+				"HTTP/1.1 400 Bad Request\n" +
+				"Content-type: text/plain\n" +
+				"Content-length: 16\n" +
+				"\n" +
+				"Bad request line"
+		);
+
+		assert httpRaw(
+				"GET"
+		).equals("" +
+				"HTTP/1.1 400 Bad Request\n" +
+				"Content-type: text/plain\n" +
+				"Content-length: 16\n" +
+				"\n" +
+				"Bad request line"
+		);
+
+		assert httpRaw("" +
+				"GET /foo HTTP/1.1\n" +
+				"Content-Length: bar\n"
+		).equals("" +
+				"HTTP/1.1 400 Bad Request\n" +
+				"Content-type: text/plain\n" +
+				"Content-length: 22\n" +
+				"\n" +
+				"Invalid content length"
+		);
+
+		assert httpRaw("" +
+				"GET /foo HTTP/1.1\n" +
+				"Content-Length: -1\n"
+		).equals("" +
+				"HTTP/1.1 400 Bad Request\n" +
+				"Content-type: text/plain\n" +
+				"Content-length: 23\n" +
+				"\n" +
+				"Negative content length"
+		);
+
+		assert httpRaw("" +
+				"GET /foo HTTP/1.1\n" +
+				"Content-Length: 3\n" +
+				"\n" +
+				"12"
+		).equals("" +
+				"HTTP/1.1 400 Bad Request\n" +
+				"Content-type: text/plain\n" +
+				"Content-length: 14\n" +
+				"\n" +
+				"Body too short"
+		);
+	}
+
+	private static void test_GET_png() throws Exception {
+		HttpURLConnection response;
+
+		response = httpGet("/png/" + getDefaultTranscoder().encode("A -> B"));
+		assert response.getResponseCode() == 200;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error") == null;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line") == null;
+		assert response.getContentType().equals("image/png");
+		assert readStreamAsImage(response.getInputStream()) != null;
+
+		response = httpGet("/plantuml/png/" + getDefaultTranscoder().encode("A -> B"));
+		assert response.getResponseCode() == 200;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error") == null;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line") == null;
+		assert response.getContentType().equals("image/png");
+		assert readStreamAsImage(response.getInputStream()) != null;
+
+		response = httpGet("/png/" + getDefaultTranscoder().encode("foo"));
+		assert response.getResponseCode() == 400;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error").equals("Syntax Error?");
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line").equals("2");
+		assert response.getContentType().equals("image/png");
+		assert readStreamAsImage(response.getErrorStream()) != null;
+	}
+
+	private static void test_GET_svg() throws Exception {
+		HttpURLConnection response;
+
+		response = httpGet("/svg/" + getDefaultTranscoder().encode("A -> B"));
+		assert response.getResponseCode() == 200;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error") == null;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line") == null;
+		assert response.getContentType().equals("image/svg+xml");
+		assert readStreamAsString(response.getInputStream()).startsWith("<?xml ");
+
+		response = httpGet("/plantuml/svg/" + getDefaultTranscoder().encode("A -> B"));
+		assert response.getResponseCode() == 200;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error") == null;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line") == null;
+		assert response.getContentType().equals("image/svg+xml");
+		assert readStreamAsString(response.getInputStream()).startsWith("<?xml ");
+
+		response = httpGet("/svg/" + getDefaultTranscoder().encode("foo"));
+		assert response.getResponseCode() == 400;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error").equals("Syntax Error?");
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line").equals("2");
+		assert response.getContentType().equals("image/svg+xml");
+		assert readStreamAsString(response.getErrorStream()).startsWith("<?xml ");
+	}
+
+	private static void test_POST_render() throws Exception {
+		HttpURLConnection response;
+
+		// Defaults to png when no format is specified
+		response = httpPostJson("/render", renderRequestJson("A -> B"));
+		assert response.getResponseCode() == 200;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error") == null;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line") == null;
+		assert response.getContentType().equals("image/png");
+		assert readStreamAsImage(response.getInputStream()) != null;
+
+		response = httpPostJson("/render", renderRequestJson("A -> B", "-tsvg"));
+		assert response.getResponseCode() == 200;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error") == null;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line") == null;
+		assert response.getContentType().equals("image/svg+xml");
+		assert readStreamAsString(response.getInputStream()).startsWith("<?xml ");
+
+		response = httpPostJson("/render", renderRequestJson("A -> B", "-ttxt"));
+		assert response.getResponseCode() == 200;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error") == null;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line") == null;
+		assert response.getContentType().equals("text/plain");
+		assert readStreamAsString(response.getInputStream()).equals("" +
+				"     ,-.          ,-.\n" +
+				"     |A|          |B|\n" +
+				"     `+'          `+'\n" +
+				"      |            | \n" +
+				"      |----------->| \n" +
+				"     ,+.          ,+.\n" +
+				"     |A|          |B|\n" +
+				"     `-'          `-'\n"
+		);
+
+		response = httpPostJson("/render", renderRequestJson("foo", "-ttxt"));
+		assert response.getResponseCode() == 200;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error").equals("Syntax Error?");
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line").equals("2");
+		assert response.getContentType().equals("text/plain");
+		assert readStreamAsString(response.getInputStream()).equals("" +
+				"[From string (line 2) ]\n" +
+				"                       \n" +
+				"@startuml              \n" +
+				"foo                    \n" +
+				"^^^^^                  \n" +
+				" Syntax Error?         \n"
+		);
+
+		response = httpPostJson("/render", renderRequestJson("@startuml", "-ttxt"));
+		assert response.getResponseCode() == 200;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error").equals("No @startuml/@enduml found");
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line").equals("0");
+		assert response.getContentType().equals("text/plain");
+		assert readStreamAsString(response.getInputStream()).equals("" +
+				"                               \n" +
+				"                               \n" +
+				"     No @startuml/@enduml found\n"
+		);
+
+		response = httpPostJson("/render", "");
+		assert response.getResponseCode() == 400;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error") == null;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line") == null;
+		assert response.getContentType().equals("text/plain");
+		assert readStreamAsString(response.getErrorStream()).equals("No request body");
+
+		response = httpPostJson("/render", "123abc");
+		assert response.getResponseCode() == 400;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error") == null;
+		assert response.getHeaderField("X-PlantUML-Diagram-Error-Line") == null;
+		assert response.getContentType().equals("text/plain");
+		assert readStreamAsString(response.getErrorStream()).contains("Error parsing request json: Unexpected character at 1:4\n");
+	}
+
+	private static void test_unknown_path() throws Exception {
+		HttpURLConnection response = httpGet("/foo");
+		assert response.getResponseCode() == 302;
+		assert response.getHeaderField("Location").equals("/plantuml/png/oqbDJyrBuGh8ISmh2VNrKGZ8JCuFJqqAJYqgIotY0aefG5G00000");
+	}
+
+	//
+	// Test DSL
+	//
+
+	private static HttpURLConnection httpGet(String path) throws Exception {
+		return urlConnection(path);
+	}
+
+	private static HttpURLConnection httpPost(String path, String contentType, byte[] content) throws Exception {
+		HttpURLConnection conn = urlConnection(path);
+		conn.setRequestMethod("POST");
+		conn.setRequestProperty("Content-Type", contentType);
+		conn.setRequestProperty("Content-Length", Integer.toString(content.length));
+		conn.setDoOutput(true);
+		conn.getOutputStream().write(content);
+		return conn;
+	}
+
+	private static HttpURLConnection httpPostJson(String path, String json) throws Exception {
+		return httpPost(path, "application/json; utf-8", json.getBytes(UTF_8));
+	}
+
+	private static String httpRaw(String request) throws Exception {
+		try (Socket socket = socketConnection()) {
+			socket.getOutputStream().write(request.getBytes(UTF_8));
+			socket.shutdownOutput();
+			return readStreamAsString(socket.getInputStream())
+					.replaceAll("\r\n", "\n");
+		}
+	}
+
+	private static BufferedImage readStreamAsImage(InputStream in) throws Exception {
+		return ImageIO.read(new MemoryCacheImageInputStream(in));
+	}
+
+	private static String readStreamAsString(InputStream in) throws IOException {
+		byte[] buffer = new byte[1024];
+		int length;
+		final ByteArrayOutputStream baos = new ByteArrayOutputStream();
+		while ((length = in.read(buffer)) != -1) {
+			baos.write(buffer, 0, length);
+		}
+		return baos.toString(UTF_8.name());
+	}
+
+	private static String renderRequestJson(String source, String... options) {
+		final JsonObject object = Json.object();
+		object.add("source", source);
+		if (options.length != 0) {
+			object.add("options", Json.array(options));
+		}
+		return object.toString();
+	}
+
+	//
+	// System under test
+	//
+
+	private static int port;
+
+	private static void startServer() throws Exception {
+		final ServerSocket serverSocket = new ServerSocket(0);
+		port = serverSocket.getLocalPort();
+
+		Thread serverLoopThread = new Thread("PicoWebServerLoop") {
+			@Override
+			public void run() {
+				try {
+					PicoWebServer.serverLoop(serverSocket);
+				} catch (IOException e) {
+					e.printStackTrace();
+				}
+			}
+		};
+
+		serverLoopThread.setDaemon(true);
+		serverLoopThread.start();
+	}
+
+	private static Socket socketConnection() throws IOException {
+		return new Socket("localhost", port);
+	}
+
+	private static HttpURLConnection urlConnection(String path) throws Exception {
+		final HttpURLConnection conn = (HttpURLConnection) new URL("http://localhost:" + port + path).openConnection();
+		conn.setInstanceFollowRedirects(false);
+		return conn;
+	}
+}

src/net/sourceforge/plantuml/picoweb/ReceivedHTTPRequest.java

@@ -0,0 +1,111 @@
+package net.sourceforge.plantuml.picoweb;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.StringTokenizer;
+
+public class ReceivedHTTPRequest {
+
+	private static final String CONTENT_LENGTH_HEADER = "content-length: ";
+
+	private String method;
+
+	private String path;
+
+	private byte[] body;
+
+	public String getMethod() {
+		return method;
+	}
+
+	public String getPath() {
+		return path;
+	}
+
+	public byte[] getBody() {
+		return body;
+	}
+
+	public static ReceivedHTTPRequest fromStream(InputStream in) throws IOException {
+		final ReceivedHTTPRequest request = new ReceivedHTTPRequest();
+
+		final String requestLine = readLine(in);
+
+		final StringTokenizer tokenizer = new StringTokenizer(requestLine);
+		if (tokenizer.countTokens() != 3) {
+			throw new BadRequest400("Bad request line");
+		}
+
+		request.method = tokenizer.nextToken().toUpperCase();
+		request.path = tokenizer.nextToken();
+
+		// Headers
+		int contentLength = 0;
+
+		while (true) {
+			String line = readLine(in);
+			if (line.isEmpty()) {
+				break;
+			} else if (line.toLowerCase().startsWith(CONTENT_LENGTH_HEADER)) {
+				contentLength = parseContentLengthHeader(line);
+			}
+		}
+
+		request.body = readBody(in, contentLength);
+		return request;
+	}
+
+	private static int parseContentLengthHeader(String line) throws IOException {
+		int contentLength;
+
+		try {
+			contentLength = Integer.parseInt(line.substring(CONTENT_LENGTH_HEADER.length()).trim());
+		} catch (NumberFormatException e) {
+			throw new BadRequest400("Invalid content length");
+		}
+
+		if (contentLength < 0) {
+			throw new BadRequest400("Negative content length");
+		}
+
+		return contentLength;
+	}
+
+	private static byte[] readBody(InputStream in, int contentLength) throws IOException {
+		if (contentLength == 0) {
+			return new byte[0];
+		}
+
+		final byte[] body = new byte[contentLength];
+		int n = 0;
+		int offset = 0;
+
+		// java.io.InputStream.readNBytes() can replace this from Java 9
+		while (n < contentLength) {
+			int count = in.read(body, offset + n, contentLength - n);
+			if (count < 0) {
+				throw new BadRequest400("Body too short");
+			}
+			n += count;
+		}
+		return body;
+	}
+
+	private static String readLine(InputStream in) throws IOException {
+		final StringBuilder builder = new StringBuilder();
+
+		while (true) {
+			int c = in.read();
+			if (c == -1 || c == '\n') {
+				break;
+			}
+			builder.append((char) c);
+		}
+
+		if (builder.length() > 0 && builder.charAt(builder.length() - 1) == '\r') {
+			builder.deleteCharAt(builder.length() - 1);
+		}
+
+		return builder.toString();
+	}
+}

src/net/sourceforge/plantuml/picoweb/RenderRequest.java

@@ -0,0 +1,45 @@
+package net.sourceforge.plantuml.picoweb;
+
+import net.sourceforge.plantuml.json.Json;
+import net.sourceforge.plantuml.json.JsonArray;
+import net.sourceforge.plantuml.json.JsonObject;
+
+/**
+ * POJO of the json sent to "POST /render"
+ */
+public class RenderRequest {
+
+	private final String[] options;
+
+	private final String source;
+
+	public RenderRequest(String[] options, String source) {
+		this.options = options;
+		this.source = source;
+	}
+
+	public String[] getOptions() {
+		return options;
+	}
+
+	public String getSource() {
+		return source;
+	}
+
+	public static RenderRequest fromJson(String json) {
+		final JsonObject parsed = Json.parse(json).asObject();
+		final String[] options;
+
+		if (parsed.contains("options")) {
+			final JsonArray jsonArray = parsed.get("options").asArray();
+			options = new String[jsonArray.size()];
+			for (int i = 0; i < jsonArray.size(); i++) {
+				options[i] = jsonArray.get(i).asString();
+			}
+		} else {
+			options = new String[0];
+		}
+
+		return new RenderRequest(options, parsed.get("source").asString());
+	}
+}