Random
using-lishys-notes.notes

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RandomService.java
package com.lishman.random.service;

import java.util.List;

import com.lishman.random.web.RandomData;


public interface RandomService {
    
    public int randomNumber();
    
    public int randomNumberInRange(int startOfRange, int endOfRange);

    public RandomData randomData();
    
    public List<Integer> randomNumberList();
}
RandomServiceImpl.java
package com.lishman.random.service;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import org.springframework.stereotype.Service;

import com.lishman.random.web.RandomData;


@Service
public class RandomServiceImpl implements RandomService {

    public int randomNumber() {
        return new Random().nextInt();        
    }
    
    public int randomNumberInRange(int startOfRange, int endOfRange) {
        return new Random().nextInt(endOfRange - startOfRange) + startOfRange;        
    }

    public RandomData randomData() {  
        Random generator = new Random();      
        RandomData data = new RandomData();
        data.setBoolean(generator.nextBoolean());
        data.setDouble(generator.nextDouble());
        data.setInteger(generator.nextInt());   
        return data;        
    }
    
    public List<Integer> randomNumberList() {
        Random generator = new Random();        
        List<Integer> numbers = new ArrayList<Integer>(10);
        for (int i=0; i<10; i++) {
            numbers.add(generator.nextInt());
        }        
        return numbers;
    } 
    
}
RandomController.java
package com.lishman.random.web;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;

import com.lishman.random.service.RandomService;

@Controller
public class RandomController {
    
    @Autowired
    private RandomService random;

    @RequestMapping("/random.html")
    @ModelAttribute("randomNumber") public int randomNumber() {
        return random.randomNumber();        
    }
    
    @RequestMapping(value="/random.html", params={"start", "end"})
    public ModelAndView randomNumberInRange(@RequestParam("start") int startOfRange,
                                            @RequestParam("end") int endOfRange) {
        int result = random.randomNumberInRange(startOfRange, endOfRange);     
        return new ModelAndView("random", "randomNumber", result);
    }

    @RequestMapping("/random-data.html")
    @ModelAttribute public RandomData randomData() {    
        return random.randomData();        
    }
    
    @RequestMapping("/random-list.html")
    @ModelAttribute("randomNumbers") public List<Integer> randomNumberList() {  
        return random.randomNumberList();
    } 
}
RandomData.java
package com.lishman.random.web;

public class RandomData {
    
    public boolean randomBoolean;
    public int randomInteger;
    public double randomDouble;

    public boolean isBoolean() {
        return randomBoolean;
    }

    public void setBoolean(boolean randomBoolean) {
        this.randomBoolean = randomBoolean;
    }

    public int getInteger() {
        return randomInteger;
    }

    public void setInteger(int randomInteger) {
        this.randomInteger = randomInteger;
    }

    public double getDouble() {
        return randomDouble;
    }

    public void setDouble(double randomDouble) {
        this.randomDouble = randomDouble;
    }
    

}
random-data.jsp
<html>
  <body>
  
    <h1>Random Data</h1>
    
    <p>A random boolean is ${randomData.boolean}</p>
    <p>A random double is ${randomData.double}</p>
    <p>A random integer is ${randomData.integer}</p>
    
    <p><a href="../index.html">Back</a></p>
    
  </body>
</html>
random-list.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>  

<html>
  <body>
  
    <h1>Random Numbers</h1>
    <p>Here are 10 random numbers:</p>
    
    <c:forEach items="${randomNumbers}" var="randomNumber">
      <div>${randomNumber}</div>
    </c:forEach>
      
    <p><a href="../index.html">Back</a></p>

  </body>
</html>
random.jsp
<html>
  <body>
  
    <h1>Random Number</h1>
    <p>A random number is ${randomNumber}</p>
    
    <p><a href="../index.html">Back</a></p>
    
  </body>
</html>
random-servlet.xml
<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
           http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
           http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd">

  <context:component-scan base-package="com.lishman.random.web"/>
  <context:component-scan base-package="com.lishman.random.service"/>
  
  <bean id="viewResolver"
        class="org.springframework.web.servlet.view.InternalResourceViewResolver"
        p:prefix="/WEB-INF/jsp/"
        p:suffix=".jsp"/>
        
</beans>
web.xml
<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://java.sun.com/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
         id="WebApp_ID"
         version="2.5">
  
  <display-name>Random</display-name>
  
  <servlet>
    <servlet-name>random</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>

  <servlet-mapping>
    <servlet-name>random</servlet-name>
    <url-pattern>/app/*</url-pattern>
  </servlet-mapping>
  
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>
  
</web-app>
index.html
<html>
  <body>
  
    <h1>Randomizer</h1>
   
    <p>
      <a href="app/random.html">Random number</a><br/>
      
      <a href="app/random.html?start=1000&end=1040">Random number in range</a><br/> 
           
      <a href="app/random-data.html">Random data</a><br/>
      
      <a href="app/random-list.html">List of random numbers</a>
    </p>
 
  </body>
</html>
server.log
INFO: Mapped URL path [/random.html] onto handler 'randomController'
INFO: Mapped URL path [/random-data.html] onto handler 'randomController'
INFO: Mapped URL path [/random-list.html] onto handler 'randomController'

Application Overview

Random is a simple application designed to demonstrate basic MVC functionality in Spring.
The user can request a single random numberrandom.html", a random number within a rangerandom.html?, different types of random datarandom-data or a list of random numbersrandom-list.
Results are displayed on one of three JSP pages, depending the type of data to be presented.
We use component scanningcomponent-scan to detect our services and controllers, and specify the location of the JSP files/WEB-INF/jsp/ to be used during view resolution.
Our controller responds to requests for random numbers using the RandomServiceRandomService:eq(1) implementation, which is injected into the controller during initialization.



Controller Details

The randomNumber()randomNumber:eq(1) method is triggered by a request to the /random.html/random.html:eq(0) URL path.

RandomServiceRandomService:eq(1) is used to produce a single random number which is added to the model as the randomNumberrandomNumber:eq(0) attribute.

No view name is specified by this method so DefaultRequestToViewNameTranslator is used to derive it from the URL/random.html:eq(0).
random.jsp displays the randomNumberp:lt(2) attribute from the model.
randomNumberInRangerandomNumberInRange:eq(0) is also associated with the /random.html/random.html:eq(1) path, but requests will only arrive at this method if the startstart:eq(0) and endend:eq(0) request parameters are present.
This method is executed by the second optionstart=1000 on the index.html page.
@RequestParam annotations set the startOfRange and endOfRange method parameters to the values in the start and end request parameters.

This time we use a ModelAndViewModelAndView:last object to return the view name and the model data.
randomDatarandomData:first returns an instance of the RandomData class which is bound to the model using a default name of randomData.
We can see how this objectp:lt(6) is accessed from the model on the random-data.jsp page.
A ListInteger of random numbers is added to the model by randomNumberListrandomNumberList:first.
random-list.jsp uses the standard JSTL forEach tag to display the results.
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