BAEL-305 - front controller pattern source

enterprise-patterns/front-controller-pattern/pom.xml

@@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>front-controller-pattern</artifactId>
+    <packaging>war</packaging>
+
+    <parent>
+        <artifactId>enterprise-patterns-parent</artifactId>
+        <groupId>com.baeldung.enterprise.patterns</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>javax.servlet</groupId>
+            <artifactId>javax.servlet-api</artifactId>
+            <version>3.1.0</version>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+            <plugin>
+                <groupId>org.eclipse.jetty</groupId>
+                <artifactId>jetty-maven-plugin</artifactId>
+                <version>9.4.0.M1</version>
+                <configuration>
+                    <webApp>
+                        <contextPath>/front-controller</contextPath>
+                    </webApp>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/FrontControllerServlet.java

@@ -0,0 +1,45 @@
+package com.baeldung.enterprise.patterns.front.controller;
+
+import com.baeldung.enterprise.patterns.front.controller.commands.FrontCommand;
+import com.baeldung.enterprise.patterns.front.controller.commands.UnknownCommand;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+public class FrontControllerServlet extends HttpServlet {
+    @Override
+    protected void doGet(
+      HttpServletRequest request,
+      HttpServletResponse response
+    ) throws ServletException, IOException {
+        FrontCommand command = getCommand(request);
+        command.init(getServletContext(), request, response);
+        command.process();
+    }
+
+    private FrontCommand getCommand(HttpServletRequest request) {
+        try {
+            return (FrontCommand) getCommandClass(request)
+              .asSubclass(FrontCommand.class)
+              .newInstance();
+        } catch (Exception e) {
+            throw new RuntimeException("Failed to get command!", e);
+        }
+    }
+
+    private Class getCommandClass(HttpServletRequest request) {
+        try {
+            return Class.forName(
+              String.format(
+                "com.baeldung.enterprise.patterns.front.controller.commands.%sCommand",
+                request.getParameter("command")
+              )
+            );
+        } catch (ClassNotFoundException e) {
+            return UnknownCommand.class;
+        }
+    }
+}

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/commands/FrontCommand.java

@@ -0,0 +1,32 @@
+package com.baeldung.enterprise.patterns.front.controller.commands;
+
+import javax.servlet.RequestDispatcher;
+import javax.servlet.ServletContext;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+public abstract class FrontCommand {
+    protected ServletContext context;
+    protected HttpServletRequest request;
+    protected HttpServletResponse response;
+
+    public void init(
+      ServletContext servletContext,
+      HttpServletRequest servletRequest,
+      HttpServletResponse servletResponse
+    ) {
+        this.context = servletContext;
+        this.request = servletRequest;
+        this.response = servletResponse;
+    }
+
+    public abstract void process() throws ServletException, IOException;
+
+    protected void forward(String target) throws ServletException, IOException {
+        target = String.format("/WEB-INF/jsp/%s.jsp", target);
+        RequestDispatcher dispatcher = context.getRequestDispatcher(target);
+        dispatcher.forward(request, response);
+    }
+}

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/commands/SearchCommand.java

@@ -0,0 +1,21 @@
+package com.baeldung.enterprise.patterns.front.controller.commands;
+
+import com.baeldung.enterprise.patterns.front.controller.data.Book;
+import com.baeldung.enterprise.patterns.front.controller.data.BookshelfImpl;
+
+import javax.servlet.ServletException;
+import java.io.IOException;
+
+public class SearchCommand extends FrontCommand {
+    @Override
+    public void process() throws ServletException, IOException {
+        Book book = new BookshelfImpl().getInstance()
+          .findByTitle(request.getParameter("title"));
+        if (book != null) {
+            request.setAttribute("book", book);
+            forward("book-found");
+        } else {
+            forward("book-notfound");
+        }
+    }
+}

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/commands/UnknownCommand.java

@@ -0,0 +1,11 @@
+package com.baeldung.enterprise.patterns.front.controller.commands;
+
+import javax.servlet.ServletException;
+import java.io.IOException;
+
+public class UnknownCommand extends FrontCommand {
+    @Override
+    public void process() throws ServletException, IOException {
+        forward("unknown");
+    }
+}

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/data/Book.java

@@ -0,0 +1,40 @@
+package com.baeldung.enterprise.patterns.front.controller.data;
+
+public class Book {
+    private String author;
+    private String title;
+    private Double price;
+
+    public Book() {
+    }
+
+    public Book(String author, String title, Double price) {
+        this.author = author;
+        this.title = title;
+        this.price = price;
+    }
+
+    public String getAuthor() {
+        return author;
+    }
+
+    public void setAuthor(String author) {
+        this.author = author;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public Double getPrice() {
+        return price;
+    }
+
+    public void setPrice(Double price) {
+        this.price = price;
+    }
+}

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/data/Bookshelf.java

@@ -0,0 +1,15 @@
+package com.baeldung.enterprise.patterns.front.controller.data;
+
+public interface Bookshelf {
+
+    default void init() {
+        add(new Book("Wilson, Robert Anton & Shea, Robert", "Illuminati", 9.99));
+        add(new Book("Fowler, Martin", "Patterns of Enterprise Application Architecture", 27.88));
+    }
+
+    Bookshelf getInstance();
+
+    <E extends Book> boolean add(E book);
+
+    Book findByTitle(String title);
+}

enterprise-patterns/front-controller-pattern/src/main/java/com/baeldung/enterprise/patterns/front/controller/data/BookshelfImpl.java

@@ -0,0 +1,24 @@
+package com.baeldung.enterprise.patterns.front.controller.data;
+
+import java.util.ArrayList;
+
+public class BookshelfImpl extends ArrayList<Book> implements Bookshelf {
+    private static Bookshelf INSTANCE;
+
+    @Override
+    public Bookshelf getInstance() {
+        if (INSTANCE == null) {
+            INSTANCE = new BookshelfImpl();
+            INSTANCE.init();
+        }
+        return INSTANCE;
+    }
+
+    @Override
+    public Book findByTitle(String title) {
+        return this.stream()
+          .filter(book -> book.getTitle().toLowerCase().contains(title.toLowerCase()))
+          .findFirst()
+          .orElse(null);
+    }
+}

enterprise-patterns/front-controller-pattern/src/main/webapp/WEB-INF/jsp/book-found.jsp

@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <title>Bookshelf: Title found</title>
+    </head>
+    <body>
+        <p>Our Bookshelf contains this title:</p>
+        <h2>${book.getTitle()}</h2>
+        <p>Author: ${book.getAuthor()}</p>
+        <input type="submit" value="Buy it: ${book.getPrice()}$">
+    </body>
+</html>

enterprise-patterns/front-controller-pattern/src/main/webapp/WEB-INF/jsp/book-notfound.jsp

@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <title>Bookshelf: Title not found</title>
+</head>
+    <body>
+        <p>Our Bookshelf doesn't contains this title:</p>
+        <h2>${param.get("title")}</h2>
+    </body>
+</html>

enterprise-patterns/front-controller-pattern/src/main/webapp/WEB-INF/jsp/unknown.jsp

@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <title>Bookshelf: Command unknown</title>
+    </head>
+    <body>
+        <p>Sorry, this command is not known!</p>
+    </body>
+</html>

enterprise-patterns/front-controller-pattern/src/main/webapp/WEB-INF/web.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
+		   http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
+         version="3.1">
+    <servlet>
+        <servlet-name>front-controller</servlet-name>
+        <servlet-class>com.baeldung.enterprise.patterns.front.controller.FrontControllerServlet</servlet-class>
+    </servlet>
+    <servlet-mapping>
+        <servlet-name>front-controller</servlet-name>
+        <url-pattern>/</url-pattern>
+    </servlet-mapping>
+</web-app>

enterprise-patterns/pom.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.baeldung.enterprise.patterns</groupId>
+    <artifactId>enterprise-patterns-parent</artifactId>
+    <packaging>pom</packaging>
+    <modules>
+        <module>front-controller-pattern</module>
+    </modules>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <build>
+        <pluginManagement>
+            <plugins>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-compiler-plugin</artifactId>
+                    <version>3.5.1</version>
+                    <configuration>
+                        <source>1.8</source>
+                        <target>1.8</target>
+                    </configuration>
+                </plugin>
+            </plugins>
+        </pluginManagement>
+    </build>
+</project>

pom.xml

@@ -29,6 +29,8 @@
         <module>dozer</module>
         <module>dependency-injection</module>
         <module>deltaspike</module>
+
+        <module>enterprise-patterns</module>
         <!-- <module>gatling</module> --> <!-- not meant to run as part of the standard build -->
 
         <module>gson</module>