simple HTTP server in Java using only Java SE API

Question

Is there a way to create a very basic HTTP server  supporting only GET POST  in Java using just the Java SE API  without writing code to manually parse HTTP requests and manually format HTTP responses  The Java SE API nicely encapsulates the HTTP client functionality in HttpURLConnection  but is there an analog for HTTP server functionality  Just to be clear  the problem I have with a lot of ServerSocket examples I ve seen online is that they do their own request parsing response formatting and error handling  which is tedious  error-prone  and not likely to be comprehensive  and I m trying to avoid it for those reasons

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Once upon a time I was looking for something similar - a lightweight yet fully functional HTTP server that I could easily embed and customize. I found two types of potential solutions:

Full servers that are not all that lightweight or simple (for an extreme definition of lightweight.)
Truly lightweight servers that aren't quite HTTP servers, but glorified ServerSocket examples that are not even remotely RFC-compliant and don't support commonly needed basic functionality.

So... I set out to write JLHTTP - The Java Lightweight HTTP Server.

You can embed it in any project as a single (if rather long) source file, or as a ~50K jar (~35K stripped) with no dependencies. It strives to be RFC-compliant and includes extensive documentation and many useful features while keeping bloat to a minimum.

Features include: virtual hosts, file serving from disk, mime type mappings via standard mime.types file, directory index generation, welcome files, support for all HTTP methods, conditional ETags and If-* header support, chunked transfer encoding, gzip/deflate compression, basic HTTPS (as provided by the JVM), partial content (download continuation), multipart/form-data handling for file uploads, multiple context handlers via API or annotations, parameter parsing (query string or x-www-form-urlencoded body), etc.

I hope others find it useful :-)

User · Answer

How about Apache Commons HttpCore project    From the web site     HttpCore Goals   Implementation of the most fundamental HTTP transport aspects Balance between good performance and the clarity  amp  expressiveness of API Small  predictable  memory footprint Self contained library  no external dependencies beyond JRE

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It s possible to create an httpserver that provides basic support for J2EE servlets with just the JDK and the servlet api in a just a few lines of code     I ve found this very useful for unit testing servlets  as it starts much faster than other lightweight containers  we use jetty for production     Most very lightweight httpservers do not provide support for servlets  but we need them  so I thought I d share   The below example provides basic servlet support  or throws and UnsupportedOperationException for stuff not yet implemented   It uses the com sun net httpserver HttpServer for basic http support   import java io    import java lang reflect    import java net InetSocketAddress  import java util     import javax servlet    import javax servlet http     import com sun net httpserver HttpExchange  import com sun net httpserver HttpHandler  import com sun net httpserver HttpServer    SuppressWarnings  deprecation   public class VerySimpleServletHttpServer       HttpServer server      private String contextPath      private HttpHandler httpHandler       public VerySimpleServletHttpServer String contextPath  HttpServlet servlet            this contextPath   contextPath          httpHandler   new HttpHandlerWithServletSupport servlet              public void start int port  throws IOException           InetSocketAddress inetSocketAddress   new InetSocketAddress port           server   HttpServer create inetSocketAddress  0           server createContext contextPath  httpHandler           server setExecutor null           server start               public void stop int secondsDelay            server stop secondsDelay              public int getServerPort             return server getAddress   getPort              final class HttpHandlerWithServletSupport implements HttpHandler        private HttpServlet servlet       private final class RequestWrapper extends HttpServletRequestWrapper           private final HttpExchange ex          private final Map lt String  String   gt  postData          private final ServletInputStream is          private final Map lt String  Object gt  attributes   new HashMap lt  gt              private RequestWrapper HttpServletRequest request  HttpExchange ex  Map lt String  String   gt  postData  ServletInputStream is                super request               this ex   ex              this postData   postData              this is   is                      Override         public String getHeader String name                return ex getRequestHeaders   getFirst name                       Override         public Enumeration lt String gt  getHeaders String name                return new Vector lt String gt  ex getRequestHeaders   get name   elements                        Override         public Enumeration lt String gt  getHeaderNames                 return new Vector lt String gt  ex getRequestHeaders   keySet    elements                        Override         public Object getAttribute String name                return attributes get name                       Override         public void setAttribute String name  Object o                this attributes put name  o                       Override         public Enumeration lt String gt  getAttributeNames                 return new Vector lt String gt  attributes keySet    elements                        Override         public String getMethod                 return ex getRequestMethod                        Override         public ServletInputStream getInputStream   throws IOException               return is                      Override         public BufferedReader getReader   throws IOException               return new BufferedReader new InputStreamReader getInputStream                          Override         public String getPathInfo                 return ex getRequestURI   getPath                        Override         public String getParameter String name                String   arr   postData get name               return arr    null    arr length  gt  1   Arrays toString arr    arr 0     null                      Override         public Map lt String  String   gt  getParameterMap                 return postData                      Override         public Enumeration lt String gt  getParameterNames                 return new Vector lt String gt  postData keySet    elements                         private final class ResponseWrapper extends HttpServletResponseWrapper           final ByteArrayOutputStream outputStream   new ByteArrayOutputStream            final ServletOutputStream servletOutputStream   new ServletOutputStream                   Override             public void write int b  throws IOException                   outputStream write b                                     private final HttpExchange ex          private final PrintWriter printWriter          private int status   HttpServletResponse SC OK           private ResponseWrapper HttpServletResponse response  HttpExchange ex                super response               this ex   ex              printWriter   new PrintWriter servletOutputStream                       Override         public void setContentType String type                ex getResponseHeaders   add  Content-Type   type                       Override         public void setHeader String name  String value                ex getResponseHeaders   add name  value                       Override         public javax servlet ServletOutputStream getOutputStream   throws IOException               return servletOutputStream                      Override         public void setContentLength int len                ex getResponseHeaders   add  Content-Length   len                            Override         public void setStatus int status                this status   status                      Override         public void sendError int sc  String msg  throws IOException               this status   sc              if  msg    null                    printWriter write msg                                     Override         public void sendError int sc  throws IOException               sendError sc  null                       Override         public PrintWriter getWriter   throws IOException               return printWriter                     public void complete   throws IOException               try                   printWriter flush                    ex sendResponseHeaders status  outputStream size                     if  outputStream size    gt  0                        ex getResponseBody   write outputStream toByteArray                                       ex getResponseBody   flush                  catch  Exception e                    e printStackTrace                  finally                   ex close                                       public HttpHandlerWithServletSupport HttpServlet servlet            this servlet   servlet              SuppressWarnings  deprecation        Override     public void handle final HttpExchange ex  throws IOException           byte   inBytes   getBytes ex getRequestBody             ex getRequestBody   close            final ByteArrayInputStream newInput   new ByteArrayInputStream inBytes           final ServletInputStream is   new ServletInputStream                   Override             public int read   throws IOException                   return newInput read                                      Map lt String  String   gt  parsePostData   new HashMap lt  gt              try               parsePostData putAll HttpUtils parseQueryString ex getRequestURI   getQuery                      check if any postdata to parse             parsePostData putAll HttpUtils parsePostData inBytes length  is              catch  IllegalArgumentException e                   no postData - just reset inputstream             newInput reset                      final Map lt String  String   gt  postData   parsePostData           RequestWrapper req   new RequestWrapper createUnimplementAdapter HttpServletRequest class   ex  postData  is            ResponseWrapper resp   new ResponseWrapper createUnimplementAdapter HttpServletResponse class   ex            try               servlet service req  resp               resp complete              catch  ServletException e                throw new IOException e                        private static byte   getBytes InputStream in  throws IOException           ByteArrayOutputStream out   new ByteArrayOutputStream            byte   buffer   new byte 1024           while  true                int r   in read buffer               if  r    -1                  break              out write buffer  0  r                     return out toByteArray                SuppressWarnings  unchecked       private static  lt T gt  T createUnimplementAdapter Class lt T gt  httpServletApi            class UnimplementedHandler implements InvocationHandler                Override             public Object invoke Object proxy  Method method  Object   args  throws Throwable                   throw new UnsupportedOperationException  Not implemented      method      args     Arrays toString args                                     return  T  Proxy newProxyInstance UnimplementedHandler class getClassLoader                    new Class lt   gt      httpServletApi                    new UnimplementedHandler

User · Answer

Check out NanoHttpd  NanoHTTPD is a light-weight HTTP server designed for embedding in other applications  released under a Modified BSD licence   It is being developed at Github and uses Apache Maven for builds  amp  unit testing quot

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This code is better than ours  you only need to add 2 libs  javax servelet jar and org mortbay jetty jar    Class Jetty   package jetty   import java util logging Level  import java util logging Logger  import org mortbay http SocketListener  import org mortbay jetty Server  import org mortbay jetty servlet ServletHttpContext   public class Jetty        public static void main String   args            try               Server server   new Server                SocketListener listener   new SocketListener                       System out println  Max Thread      listener getMaxThreads       Min Thread      listener getMinThreads                  listener setHost  localhost                listener setPort 8070               listener setMinThreads 5               listener setMaxThreads 250               server addListener listener                            ServletHttpContext context    ServletHttpContext  server getContext                   context addServlet   MO    jetty HelloWorldServlet                 server start                server join                 We will create our server running at http   localhost 8070         Server server   new Server            server addListener   8070               We will deploy our servlet to the server at the path               it will be available at http   localhost 8070         ServletHttpContext context    ServletHttpContext  server getContext               context addServlet   MO    jetty HelloWorldServlet             server start                          catch  Exception ex                Logger getLogger Jetty class getName    log Level SEVERE  null  ex                         Servlet class       package jetty   import java io IOException  import java io PrintWriter  import javax servlet ServletException  import javax servlet http HttpServlet  import javax servlet http HttpServletRequest  import javax servlet http HttpServletResponse   public class HelloWorldServlet extends HttpServlet        Override     protected void doGet HttpServletRequest httpServletRequest  HttpServletResponse httpServletResponse  throws ServletException  IOException               String appid   httpServletRequest getParameter  appid            String conta   httpServletRequest getParameter  conta             System out println  Appid     appid           System out println  Conta     conta            httpServletResponse setContentType  text plain            PrintWriter out   httpServletResponse getWriter            out println  Hello World             out close

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The com sun net httpserver solution is not portable across JREs  Its better to use the official webservices API in javax xml ws to bootstrap a minimal HTTP server     import java io   import javax xml ws   import javax xml ws http   import javax xml transform   import javax xml transform stream     WebServiceProvider  ServiceMode value Service Mode PAYLOAD   class P extends Provider Source      def invoke source  Source    new StreamSource  new StringReader   lt p gt Hello There  lt  p gt         val address    http   127 0 0 1 8080   Endpoint create HTTPBinding HTTP BINDING  new P    publish address   println  Service running at   address  println  Type  CTRL   C  to quit     Thread sleep Long MaxValue    EDIT  this actually works  The above code looks like Groovy or something  Here is a translation to Java which I tested   import java io    import javax xml ws    import javax xml ws http    import javax xml transform    import javax xml transform stream      WebServiceProvider  ServiceMode value   Service Mode PAYLOAD  public class Server implements Provider lt Source gt         public Source invoke Source request            return  new StreamSource new StringReader   lt p gt Hello There  lt  p gt                 public static void main String   args  throws InterruptedException            String address    http   127 0 0 1 8080            Endpoint create HTTPBinding HTTP BINDING  new Server    publish address            System out println  Service running at     address           System out println  Type  CTRL   C  to quit              Thread sleep Long MAX VALUE

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All the above answers details about Single main threaded Request Handler   setting    server setExecutor java util concurrent Executors newCachedThreadPool       Allows multiple request serving via multiple threads using executor service   So the end code will be something like below   import java io IOException  import java io OutputStream  import java net InetSocketAddress  import com sun net httpserver HttpExchange  import com sun net httpserver HttpHandler  import com sun net httpserver HttpServer  public class App       public static void main String   args  throws Exception           HttpServer server   HttpServer create new InetSocketAddress 8000   0           server createContext   test   new MyHandler               Thread control is given to executor service          server setExecutor java util concurrent Executors newCachedThreadPool             server start              static class MyHandler implements HttpHandler            Override         public void handle HttpExchange t  throws IOException               String response    This is the response               long threadId   Thread currentThread   getId                System out println  I am thread     threadId                response   response    Thread Id     threadId              t sendResponseHeaders 200  response length                 OutputStream os   t getResponseBody                os write response getBytes                 os close

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Spark is the simplest  here is a quick start guide  http   sparkjava com

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You can write a pretty simple embedded Jetty Java server   Embedded Jetty means that the server  Jetty  shipped together with the application as opposed of deploying the application on external Jetty server   So if in non-embedded approach your webapp built into WAR file which deployed to some external server  Tomcat   Jetty   etc   in embedded Jetty  you write the webapp and instantiate the jetty server in the same code base   An example for embedded Jetty Java server you can git clone and use  https   github com stas-slu embedded-jetty-java-server-example

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You may also have a look at some NIO application framework such as     Netty  http   jboss org netty Apache Mina  http   mina apache org  or its subproject AsyncWeb  http   mina apache org asyncweb

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Check out takes  Look at https   github com yegor256 takes for quick info

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checkout Simple  its a pretty simple embeddable server with built in support for quite a variety of operations  I particularly love its threading model    Amazing

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Try this https   github com devashish234073 Java-Socket-Http-Server blob master README md  This API has creates an HTTP server using sockets     It gets a request from the browser as text Parses it to retrieve URL info  method  attributes  etc  Creates dynamic response using the URL mapping defined Sends the response to the browser    For example the here s how the constructor in the Response java class  converts a raw response into an http response   public Response String resp       Date date   new Date        String start    HTTP 1 1 200 OK r n       String header    Date    date toString     r n       header    Content-Type  text html r n       header    Content-length    resp length     r n       header    r n       this resp start header resp

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I can strongly recommend looking into Simple  especially if you don t need Servlet capabilities but simply access to the request reponse objects  If you need REST you can put Jersey on top of it  if you need to output HTML or similar there s Freemarker  I really love what you can do with this combination  and there is relatively little API to learn

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I like this question because this is an area where there s continuous innovation and there s always a need to have a light server especially when talking about embedded servers in small er  devices   I think answers fall into two broad groups    Thin-server  server-up static content with minimal processing  context or session processing  Small-server  ostensibly a has many httpD-like server qualities with as small a footprint as you can get away with    While I might consider HTTP libraries like  Jetty  Apache Http Components  Netty and others to be more like  a raw HTTP processing facilities  The labelling is very subjective  and depends on the kinds of thing you ve been call-on to deliver for small-sites   I make this distinction in the spirit of the question  particularly the remark about          without writing code to manually parse HTTP requests and manually format HTTP responses       These raw tools let you do that  as described in other answers    They don t really lend themselves to a ready-set-go style of making a light  embedded or mini-server   A mini-server is something that can give you similar functionality to a full-function web server  like say  Tomcat  without bells and whistles  low volume  good performance 99  of the time   A thin-server seems closer to the original phrasing just a bit more than raw perhaps with a limited subset functionality  enough to make you look good 90  of the time   My idea of raw would be makes me look good 75  - 89  of the time without extra design and coding   I think if when you reach the level of WAR files  we ve left the  small  for bonsi servers that looks like everything a big server does smaller   Thin-server options   Grizzly  UniRest  multiple-languages  NanoHTTPD  just one file    Mini-server options    Spark Java     Good things are possible with lots of helper constructs like Filters  Templates  etc  MadVoc     aims to be bonsai and could well be such   -    Among the other things to consider  I d include authentication  validation  internationalisation  using something like FreeMaker or other template tool to render page output   Otherwise managing HTML editing and parameterisation is likely to make working with HTTP look like noughts-n-crosses    Naturally it all depends on how flexible you need to be   If it s a menu-driven FAX machine it can be very simple   The more interactions  the  thicker  your framework needs to be  Good question  good luck

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Since Java SE 6  there s a builtin HTTP server in Sun Oracle JRE  The com sun net httpserver package summary outlines the involved classes and contains examples   Here s a kickoff example copypasted from their docs  to all people trying to edit it nonetheless  because it s an ugly piece of code  please don t  this is a copy paste  not mine  moreover you should never edit quotations unless they have changed in the original source   You can just copy n paste n run it on Java 6     package com stackoverflow q3732109   import java io IOException  import java io OutputStream  import java net InetSocketAddress   import com sun net httpserver HttpExchange  import com sun net httpserver HttpHandler  import com sun net httpserver HttpServer   public class Test        public static void main String   args  throws Exception           HttpServer server   HttpServer create new InetSocketAddress 8000   0           server createContext   test   new MyHandler             server setExecutor null      creates a default executor         server start               static class MyHandler implements HttpHandler            Override         public void handle HttpExchange t  throws IOException               String response    This is the response               t sendResponseHeaders 200  response length                 OutputStream os   t getResponseBody                os write response getBytes                 os close                          Noted should be that the response length   part in their example is bad  it should have been response getBytes   length  Even then  the getBytes   method must explicitly specify the charset which you then specify in the response header  Alas  albeit misguiding to starters  it s after all just a basic kickoff example   Execute it and go to http   localhost 8000 test and you ll see the following response      This is the response     As to using com sun   classes  do note that this is  in contrary to what some developers think  absolutely not forbidden by the well known FAQ Why Developers Should Not Write Programs That Call  sun  Packages  That FAQ concerns the sun   package  such as sun misc BASE64Encoder  for internal usage by the Oracle JRE  which would thus kill your application when you run it on a different JRE   not the com sun   package  Sun Oracle also just develop software on top of the Java SE API themselves like as every other company such as Apache and so on  Using com sun   classes is only discouraged  but not forbidden  when it concerns an implementation of a certain Java API  such as GlassFish  Java EE impl   Mojarra  JSF impl   Jersey  JAX-RS impl   etc

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Have a look at the  Jetty  web server Jetty  Superb piece of Open Source software that would seem to meet all your requirments   If you insist on rolling your own then have a look at the  httpMessage  class

[java] simple HTTP server in Java using only Java SE API

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