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...

Let's get to work on the Index page and template. Make Index.tml look like this:

Code Block

lang	xml
title	Index.tml
lang	xml

<html t:type="layout" title="Hi/Lo Guess"
  xmlns:t="http://tapestry.apache.org/schema/tapestry_5_3.xsd">

  <p>
    I'm thinking of a number between one and ten ... </p>

  <p>
    <a href="#">start guessing</a>
  </p>

</html>

And edit the corresponding Java class, Index.java, removing its body (but leaving the imports in place for now):

Code Block

langtitle	Index.java
titlelang	Index.java

public class Index
{
}

...

First, the component. We want to perform an action (selecting the number) before continuing on to the Guess page. The ActionLink component is just what we need; it creates a link with a URL that will trigger an action event in our code ... but that's getting ahead of ourselves. First up, convert the \<a\> tag to an ActionLink component:

xml

Code Block

lang

title	Index.tml (partial)
lang	xml

  <p>
    <t:actionlink t:id="start">start guessing</t:actionlink>
  </p>

...

When handling a component event request (the kind of request triggered by the ActionLink component's URL), Tapestry will find the component and trigger a component event on it. This is the callback our server-side code needs to figure out what the user is doing on the client side. Let's start with an empty event handler:

Code Block

langtitle	Index.java
titlelang	Index.java

package com.example.tutorial.pages;

public class Index
{
  void onActionFromStart()
  {

  }
}

...

How about this: add the @Log annotation to the method:

java

Code Block

lang

title	Index.java (partial)
lang	java

  import org.apache.tapestry5.annotations.Log;

  . . .

  @Log
  void onActionFromStart()
  {

  }

...

With that in mind, we can modify Index to invoke this new setup() method:

java

Code Block

lang

title	Index.java (revised)
lang	java

package com.example.tutorial.pages;

import java.util.Random;

import org.apache.tapestry5.annotations.InjectPage;
import org.apache.tapestry5.annotations.Log;

public class Index
{
  private final Random random = new Random(System.nanoTime());

  @InjectPage
  private Guess guess;

  @Log
  Object onActionFromStart()
  {
    int target = random.nextInt(10) + 1;

    guess.setup(target);

    return guess;
  }
}

...

Ah! We didn't create a Guess page template. Tapestry was really expecting us to create one, so we better do so.

xml

Code Block

lang

title	src/main/resources/com/example/tutorial/pages/Guess.tml
lang	xml

<html t:type="layout" title="Guess The Number"
  xmlns:t="http://tapestry.apache.org/schema/tapestry_5_3.xsd">

  <p>
  The secret number is: ${target}.
  </p>
  
</html>

...

When building Tapestry pages, you sometimes start with the Java code and build the template to match, and sometime start with the template and build the Java code to match. Both approaches are valid. Here, lets start with the markup in the template, then figure out what we need in the Java code to make it work.

xml

Code Block

lang

title	Guess.tml (revised)
lang	xml

<html t:type="layout" title="Guess The Number"
  xmlns:t="http://tapestry.apache.org/schema/tapestry_5_3.xsd"
  xmlns:p="tapestry:parameter">

  <p:sidebar>
    <p>
      The secret number is: ${target}.
  </p>
  </p:sidebar>

  <strong>Guess #${guessCount}</strong>

  <p>Make a guess from the options below:</p>

  <ul>
    <t:loop source="1..10" value="current">
      <li>
        <t:actionlink t:id="makeGuess" context="current">${current}
        </t:actionlink>
      </li>
    </t:loop>
  </ul>

</html>

...

Info
The URL for the ActionLink will be `/tutorial1/guess.makeguess/3`. That's the page name, "Guess", the component id, "makeGuess", and the context value, "3".

java

Code Block

lang

title	Guess.java (revised)
lang	java

package com.example.tutorial.pages;

import org.apache.tapestry5.annotations.Persist;
import org.apache.tapestry5.annotations.Property;

public class Guess
{
  @Property
  @Persist
  private int target, guessCount;

  @Property
  private int current;

  void setup(int target)
  {
    this.target = target;
    guessCount = 1;
  }

  void onActionFromMakeGuess(int value)
  {
    guessCount++;
  }

}

...

Let's start with the Guess page; it now needs a new property to store the message to be displayed to the user, and needs a field for the injected GameOver page:

java

Code Block

lang

title	Guess.java (partial)
lang	java

  @Property
  @Persist(PersistenceConstants.FLASH)
  private String message;

  @InjectPage
  private GameOver gameOver;

...

Next, we need some more logic in the onActionFromMakeGuess() event handler method:

java

Code Block

lang

title	Guess.java (partial)
lang	java

  Object onActionFromMakeGuess(int value)
  {
    if (value == target)
    {
      gameOver.setup(target, guessCount);
      return gameOver;
    }

    guessCount++;

    message = String.format("Your guess of %d is too %s.", value,
        value < target ? "low" : "high");

    return null;
  }

...

In the template, we just need to add some markup to display the message:

xml

Code Block

lang

title	Guess.tml (partial)
lang	xml

  <strong>Guess #${guessCount}</strong>

  <t:if test="message">
    <p>
      <strong>${message}</strong>
    </p>
  </t:if>

...

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