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[Java教程]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

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

  

 

效果:

 

  

 

 

。。