Play Framework 完整实现一个APP（六）

需要为Blog添加查看和发表评论的功能

1.创建查看功能

Application.java中添加 show() 方法

public static void show(Long id) {
    Post post = Post.findById(id);
    render(post);
}

创建 app/views/Application/show.html

#{extends 'main.html' /}
#{set title:post.title /}
 
#{display post:post, as:'full' /}

在页面模板中添加链接

访问Blog

<h2 class="post-title">
    <a href="@{Application.show(_post.id)}">${_post.title}</a>
</h2>

返回主页

<h1><a href="@{Application.index()}">${blogTitle}</a></h1>

2.创建路由规则

当前页面URL http://localhost:9000/application/show?id=3

是由 * /{controller}/{action} {controller}.{action} 这条规则解析得到的

在之前新创建Route

GET     /posts/{id}                             Application.show

访问路径变为 http://localhost:9000/posts/3

更多路由语法参考： http://play-framework.herokuapp.com/zh/routes#syntax

3.添加页导航

Post类添加方法，previous() ext()

public Post previous() {
    return Post.find("postedAt < ? order by postedAt desc", postedAt).first();
}
 
public Post next() {
    return Post.find("postedAt > ? order by postedAt asc", postedAt).first();
}

show.html页面添加导航按钮

<ul id="pagination">
    #{if post.previous()}
        <li id="previous">
            <a href="@{Application.show(post.previous().id)}">
                ${post.previous().title}
            </a>
        </li>
    #{/if}
    #{if post.next()}
        <li id="next">
            <a href="@{Application.show(post.next().id)}">
                ${post.next().title}
            </a>
        </li>
    #{/if}
</ul>

4.添加评论框

Application Controller添加方法postComment()

public static void postComment(Long postId, String author, String content) {
    Post post = Post.findById(postId);
    post.addComment(author, content);
    show(postId);
}

修改show.html

<h3>Post a comment</h3>
 
#{form @Application.postComment(post.id)}
    <p>
        <label for="author">Your name: </label>
        <input type="text" name="author" id="author" />
    </p>
    <p>
        <label for="content">Your message: </label>
        <textarea name="content" id="content"></textarea>
    </p>
    <p>
        <input type="submit" value="Submit your comment" />
    </p>
#{/form}

5.添加验证，验证Author和Content非空

import play.data.validation.*;

public static void postComment(Long postId, @Required String author, @Required String content) {
    Post post = Post.findById(postId);
    if (validation.hasErrors()) {
        render("Application/show.html", post);
    }
    post.addComment(author, content);
    show(postId);
}

编辑form，显示错误

#{form @Application.postComment(post.id)}
 
    #{ifErrors}
        <p class="error">
            All fields are required!
        </p>
    #{/ifErrors}
 
    <p>
        <label for="author">Your name: </label>
        <input type="text" name="author" id="author" value="${params.author}" />
    </p>
    <p>
        <label for="content">Your message: </label>
        <textarea name="content" id="content">${params.content}</textarea>
    </p>
    <p>
        <input type="submit" value="Submit your comment" />
    </p>
#{/form}

6.优化客户提示

加载jquery的类库

修改Show.html

#{if flash.success} 
　　<p class="success">${flash.success}</p> 
#{/if} 

#{display post:post, as:'full' /}

<script type="text/javascript" charset="utf-8">
    $(function() {         
        // Expose the form 
        $('form').click(function() { 
            $('form').expose({api: true}).load(); 
        }); 
        
        // If there is an error, focus to form
        if($('form .error').size()) {
            $('form').expose({api: true, loadSpeed: 0}).load(); 
            $('form input[type=text]').get(0).focus();
        }
    });
</script>

添加Comment成功的提示

post.addComment(author, content);
flash.success("Thanks for posting %s", author);

添加路由

POST    /posts/{postId}/comments                Application.postComment