Servlet IO - Convert your servlets to MVC controllers

Supported since Servlet 3.0.1

Getting Started

Add the jitpack.io repository

<repository>
    <id>jitpack.io</id>
    <url>https://jitpack.io</url>
</repository>

Add as a maven dependency

<dependency>
    <groupId>com.github.zerh</groupId>
    <artifactId>servlet-io</artifactId>
    <version>3.1-bb94161f41-1</version>
</dependency>

Add ”/*“ to your mapped url, example: @WebServlet("/your-path/*"), and replace the super class HttpServlet by ServletIO.

import javax.servlet.annotation.WebServlet;

import com.github.zerh.servletio.*;
import com.github.zerh.servletio.annotation.Get;

@WebServlet("/base-path/*")
public class MyApp extends ServletIO {
    
    @Get("/hello")
    public Result index(Request req){
        return respond("<h1>hello world</h1>").as("text/html");
    }
}

Also the parameters could be mapped in the url:

import javax.servlet.annotation.WebServlet;

import com.github.zerh.servletio.*;
import com.github.zerh.servletio.annotation.Get;

@WebServlet("/base-path/*")
public class MyApp extends ServletIO {
    
    @Get("/edit/:id")
    public Result edit(Request req){
        return respond("<h1>the url has: " + req.param(":id") + "</h1>").as("text/html");
    }
}

Of course, you also can use:

• @Post
• @Put
• @Delete
• @Options

Result

Result is just an elegant way to declare controllers methods. The Result object wraps with ServletIO the methods printers of the Response object, to produce standard HTTP results. The methodsas(String contentType), withCookies(Cookies... cookies) and withDiscardingCookies(Cookies... cookies) and others returns the same instance of the Result object.

ServletIO contains some helper methods that return objects Result:

• respond(String content) returns HTTP results with the 200 code.
• internalServerError(String content) returns HTTP results with the 500 code.
• sendFile(InputStream inputStream) send file to client.
• badRequest(String optionalContent)returns HTTP results with the 400 code.
• notFound(String optionalContent) returns HTTP results with the 404 code.
• redirect(String target) redirect to the target.
• temporaryRedirect(String target) redirect to the target with 303 code

Jsp

Returning Jsp you can render a jsp file from the controller

import javax.servlet.annotation.WebServlet;

import com.github.zerh.servletio.*;
import com.github.zerh.servletio.annotation.Get;

@WebServlet("/base-path/*")
public class MyApp extends ServletIO {
    
    @Get("/myview")
    public Jsp myJspView(Request req){
        return jsp("/WEB-INF/my-view.jsp");
    }
}

@Before and @After

Methods annotated with the @Before annotation are executed before each action call for ServletIO, and methods annotated with the @After annotation are executed after each action call for the Servlet:

import javax.servlet.annotation.WebServlet;

import com.github.zerh.servletio.*;
import com.github.zerh.servletio.annotation.Get;

@WebServlet("/base-path/*")
public class MyApp extends ServletIO {

    @Get
    public Result index(Request req){
        return respond("<h1>hello world</h1>").as("text/html");
    }
    
    @Before
    public Result validateUser(Request req, Response res){
        if(req.session().attribute("user")==null)
            res.printHtml("bye bye!!");
        
        return null;
    }
    
    @After
    public Result log(Request req, Response res){
        System.out.println("Action executed...");
        
        return null;
    }
    
    @After
    public Result onNotFound(Request req){
        if(!isMapped(req))
            return notFound("<h1>404, not found</h1>").as("text/html");
        
        return null;
    }

}

If you don’t want the @Before or @After methods to intercept all request, you can specify a list of actions using only param:

import javax.servlet.annotation.WebServlet;

import com.github.zerh.servletio.*;
import com.github.zerh.servletio.annotation.Get;

@WebServlet("/base-path/*")
public class MyApp extends ServletIO {
    
    @Get
    public Result login(Request req){
    	return respond("<h1>login</h1>").as("text/html");
    }
    
    @Before(only="/admin")
    public Result validateUser(Request req, Response res){
        if(req.session().attribute("user")==null)  
            res.redirect("login");
            
        return null;
    }
    
    @After(only={"/login", "/logout"})
    public Result log(Request req, Response res){
        System.out.prinln("/login or /logout executed");
        
        return null;
    }
    
    ...
}

Or you can specify a list of actions to exclude for @After or @Before using the unless param:

import javax.servlet.annotation.WebServlet;

import com.github.zerh.servletio.*;
import com.github.zerh.servletio.annotation.Get;

@WebServlet("/base-path/*")
public class MyApp extends ServletIO {
    
    @Get
    public Jsp login(Request req){
    	return jsp("/WEB-INF/login.jsp");
    }
    
    @Before(unless="/login")
    public Result validateUser(Request req, Response res){
        if(req.session().attribute("user")==null)
            req.dispatcher("login").forward(req, res);
            
        return null;
    }
    ...
}

You can set execution priority of @Before or @After methods using priority param, example @Before(priority=1), by default priority is 0 (executed first):

import javax.servlet.annotation.WebServlet;

import com.github.zerh.servletio.*;
import com.github.zerh.servletio.annotation.Get;

@WebServlet("/base-path/*")
public class MyApp extends ServletIO {
    
    @Before(only="/admin/something", priority=2)
    public Result adminSomething(Request req, Response res){
        //some filter for this action
        
        return null;
    }
    
    @Before(only="/admin/*", priority=1)
    public Result validateUser(Request req, Response res){
        if(req.session().attribute("user")==null)
            res.redirect("login");
        
        return null;
    }
    ...
}

Request and Response

You can either use Request or Response only as method parameters. This classes wrap HttpServletRequest and HttpServletResponse and offer some facilities. The most prominents are:

Request

• request.bindParam(MyBean.class) returns an instance of MyBean with all values of HTML form, by mapping bean properties names.
• request.dispatcher(String dispatcherName) returns an instance of com.github.zerh.servletio.Dispatcher, wrap of RequestDispatcher.
• request.raw final property with HttpServletRequest object reference of the current request.

Response

• response.print(String htmlString, String contentType).
• response.print(String text) print text plain.
• response.printHtml(String htmlString) print text with HTML content type.
• response.printXml(String xmlString) print text with XML content type.
• response.printJson(String xmlString) print text with JSON content type.
• response.redirect(String location) redirect to the specified location.
• response.redirect(String location, int httpStatusCode) redirect to the specified location with status code.
• response.sendError(int error) send custom error code to the browser.
• response.sendBadRequest() sen 400 error code to the browser.
• response.sendInternalServerError() send 500 error code to the browser.
• response.raw final propierty with HttpServletResponse object reference of the current request