Play Framework 完整实现一个APP（八)

创建Tag标签

1.创建Model

@Entity
@Table(name = "blog_tag")
public class Tag extends Model implements Comparable<Tag> {

    public String name;

    private Tag(String name) {
        this.name = name;
    }

    public String toString() {
        return name;
    }

    public int compareTo(Tag otherTag) {
        return name.compareTo(otherTag.name);
    }

    public static Tag findOrCreateByName(String name) {
        Tag tag = Tag.find("byName", name).first();
        if(tag == null) {
            tag = new Tag(name);
        }
        return tag;
    }
}

2.Post类添加Tag属性

@ManyToMany(cascade = CascadeType.PERSIST)
public Set<Tag> tags;

public Post(User author, String title, String content) {
        this.comments = new ArrayList<Comment>();
        this.tags = new TreeSet<Tag>();
        this.author = author;
        this.title = title;
        this.content = content;
        this.postedAt = new Date();
}

　

3.Post类添加方法

关联Post和Tag

public Post tagItWith(String name) {
        tags.add(Tag.findOrCreateByName(name));
        return this;
}

　　

返回关联指定Tag的Post集合

public static List<Post> findTaggedWith(String... tags) {
        return Post.find(
                "select distinct p from Post p join p.tags as t where t.name in (:tags) group by p.id, p.author, p.title, p.content,p.postedAt having count(t.id) = :size"
        ).bind("tags", tags).bind("size", tags.length).fetch();
}

4.写测试用例

@Test
public void testTags() {
        // Create a new user and save it
        User bob = new User("bob@gmail.com", "secret", "Bob").save();

        // Create a new post
        Post bobPost = new Post(bob, "My first post", "Hello world").save();
        Post anotherBobPost = new Post(bob, "Hop", "Hello world").save();

        // Well
        assertEquals(0, Post.findTaggedWith("Red").size());

        // Tag it now
        bobPost.tagItWith("Red").tagItWith("Blue").save();
        anotherBobPost.tagItWith("Red").tagItWith("Green").save();

        // Check
        assertEquals(1, Post.findTaggedWith("Red", "Blue").size());
        assertEquals(1, Post.findTaggedWith("Red", "Green").size());
        assertEquals(0, Post.findTaggedWith("Red", "Green", "Blue").size());
        assertEquals(0, Post.findTaggedWith("Green", "Blue").size());
}

测试Tag

5.继续修改Tag类，添加方法

public static List<Map> getCloud() {
        List<Map> result = Tag.find(
            "select new map(t.name as tag, count(p.id) as pound) from Post p join p.tags as t group by t.name order by t.name"
        ).fetch();
        return result;
}

6.将Tag添加到页面上

/yabe/conf/initial-data.yml 添加预置数据

Tag(play):
    name:           Play

Tag(architecture):
    name:           Architecture

Tag(test):
    name:           Test

Tag(mvc):
    name:           MVC 

Post(jeffPost):
    title:          The MVC application
    postedAt:       2009-06-06
    author:         jeff
    tags:
                    - play
                    - architecture
                    - mvc
    content:        >
                    A Play

　　

7.修改display.html将tag显示出来

<div class="post-metadata">
        <span class="post-author">by ${_post.author.fullname}</span>,
        <span class="post-date">${_post.postedAt.format('dd MMM yy')}</span>
	    #{if _as != 'full'}
			<span class="post-comments">
				 |  ${_post.comments.size() ?: 'no'}
				comment${_post.comments.size().pluralize()}
				 #{if _post.comments}
				 	 , latest by ${_post.comments[0].author}
				 #{/if}
			</span>
		#{/if}
		#{elseif _post.tags}
			<span class="post-tags">
				- Tagged
				#{list items:_post.tags, as:'tag'}
					<a href="#">${tag}</a>${tag_isLast ? '' : ', '}
				#{/list}
			</span>
		#{/elseif}
 </div>

　　

8.添加listTagged 方法（Application Controller）

点击Tagged，显示所有带有Tag的Post列表

public static void listTagged(String tag) {
    List<Post> posts = Post.findTaggedWith(tag);
    render(tag, posts);
}

9.修改display.html，Tag显示

- Tagged
#{list items:_post.tags, as:'tag'}
    <a href="@{Application.listTagged(tag.name)}">${tag}</a>${tag_isLast ? '' : ', '}
#{/list}

　　

10.添加Route

GET     /posts/{tag}                    Application.listTagged

　　

现在有两条Route规则URL无法区分

GET     /posts/{id}                             Application.show
GET     /posts/{tag}                    	Application.listTagged

为{id}添加规则

GET     /posts/{<[0-9]+>id}             　　　　Application.show

　　

11.添加Post list页面，有相同Tag的Post

创建/app/views/Application/listTagged.html

#{extends 'main.html' /}
#{set title:'Posts tagged with ' + tag /}

*{********* Title ********* }*
#{if posts.size()>1}
	<h3>There are ${posts.size()} posts tagged ${tag}</h3>
#{/if}
#{elseif posts}
    <h3>There is 1 post tagged '${tag}'</h3>
#{/elseif}
#{else}
    <h3>No post tagged '${tag}'</h3>
#{/else}

*{********* Posts list *********}*
<div class="older-posts">
	#{list items:posts, as:'post'}
		#{display post:post, as:'teaser' /}
	#{/list}
</div>

　　

效果：

　　

。。