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20130517-Grails In Action-4、让模型工作(06小节)

 
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1、Criteria（条件查询）

Criteria可以通过createCriteria 或者 withCriteria 方法来使用

 1     def user = User.findByUserId(params.user)
 2     def entries = Post.createCriteria().list {
 3         and {
 4             eq('user', user)
 5             between('created', new Date()-1, new Date())
 6             tags {
 7                 eq('name', 'Grails')
 8             }
 9         }
10         maxResults(10)
11         order("created", "desc")
12     }

and:里面所有查询条件都是“与”关系（全部为真）

tags:Tag对象

maxResults:记录数

order:排序

1     def entries = Post.withCriteria {
2         and {
3             eq('user', user)
4             between('created', new Date()-1, new Date())
5         }
6     }

在系统中增加一个高级查询功能，用多条件组合查询Profile

新建一个闭包com.grailsinaction.UserController/advResults

 1     def advSearch = {
 2     }
 3 
 4     def advResults = {
 5         def profileProps = Profile.metaClass.properties*.name
 6         def profiles = Profile.withCriteria {
 7             "${params.queryType}" {
 8                 params.each { field, value ->
 9                     if (profileProps.grep(field) && value) {
10                         ilike(field, value)
11                     }
12                 }
13             }
14         }
15         [ profiles : profiles ]
16     }

新建一个查询页面views/user/advSearch.gsp

 1 <html>
 2     <head>
 3         <title>Advanced Search</title>
 4         <meta name="layout" content="main"/>
 5     </head>
 6     
 7     <body>
 8         <formset>
 9             <legend>Advanced Search for Friends</legend>
10             <table>
11                 <g:form action="advResults">
12                     <tr>
13                         <td>Name</td>
14                         <td><g:textField name="fullName" /></td>
15                     </tr>
16                     <tr>
17                         <td>Email</td>
18                         <td><g:textField name="email" /></td>
19                     </tr>
20                     <tr>
21                         <td>Homepage</td>
22                         <td><g:textField name="homepage" /></td>
23                     </tr>
24                     <tr>
25                         <td>Query Type:</td>
26                         <td>
27                             <g:radioGroup name="queryType" labels="['And','Or','Not']" values="['and','or','not']" value="and" >${it.radio} ${it.label}</g:radioGroup>
28                         </td>
29                     </tr>
30                     <tr>
31                         <td/>
32                         <td><g:submitButton name="search" value="Search"/></td>
33                     </tr>
34                 </g:form>
35             </table>
36         </formset>
37     </body>
38 </html>

新建一个查询结果返回页面views/user/advResults

 1 <html>
 2     <head>
 3         <title>Advanced Search Results</title>
 4         <meta name="layout" content="main"/>
 5     </head>
 6     
 7     <body>
 8         <h1>Advanced Results</h1>
 9         <p>Searched for items matching <em>${term}</em>. Found <strong>${profiles.size()}</strong> hits.
10         </p>
11         <ul>
12             <g:each var="profile" in="${profiles}">
13                 <li>${profile.fullName}</li>
14             </g:each>
15         </ul>
16         <g:link action='advSearch'>Search Again</g:link>
17     </body>
18 </html>

2、Projections（投影）

投影被用于定制查询结果。要使用投影你需要在criteria builder树里定义一个"projections"节点

1     def tagList = Post.withCriteria {
2         createAlias("user", "u")
3         createAlias("tags", "t")
4         eq("u.userId", "glen")
5         projections {
6             groupProperty("t.name")
7             count("t.id")
8         }
9     }

3、HQL

硬编码

def results = Book.findAll("from Book as b where b.title like 'Lord of the%'")

位置参数

def results = Book.findAll("from Book as b where b.title like ?", ["The Shi%"])

命名参数

def results = Book.findAll("from Book as b where b.title like :search or b.author like :search", [search:"The Shi%"])

多行

1 def results = Book.findAll("""\\
2 from Book as b, \\
3      Author as a \\
4 where b.author = a and a.surname = ?""", ['Smith'])

分页排序

def results = Book.findAll("from Book as b where b.title like 'Lord of the%'",  [max:10, offset:20, sort:"asc", order:"title"])

4、总结和最佳实践

  • Use scaffolds for instant gratification and to stay motivated:使用动态脚手架能给开发者带来惊喜，如果愿意就尽量使用吧
  • Understand your customization options:可以使用调整css的方法调整界面,也可以修改脚手架模板代码改善脚手架生成的外观,只要愿意
  • Dynamic finders are fantastic for two-field queries:动态查询器比较适合两个参数的查询
  • Use the Grails console:善用console可以帮助我们调试程序
  • Harness the power of criteria queries:提高使用criteria queries的能力，因为那很重要
  • Always use named params for HQL:慎用HQL,除非其他方法不能解决,如果一定要用,要使用命名参数,防止SQL注入攻击
  • Use bootstraps conditionally:使用bootstrap加入原始数据时,带入环境条件,避免测试数据在生产环境出现

5、代码清单

domain
    package:com.grailsinaction
        Post
        Profile
        User
        Tag
controllers
    package:com.grailsinactin
        PostController
        ProfileController
        UserController
        TagController
views
    layout
        main.gsp
    user
        advResults.gsp
        advSearch.gsp
        results.gsp
        search.gst
    error.gsp
test/integration
    package:com.grailsinaction
        PostIntegrationTests
        UserIntegrationTests
        QueryIntegrationTests
web-app
    css
        hubbub.css
    images
        backgroud.png
        headerlogo.png

6、代码打包下载

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20130515-Grails In Action-3、建模(04小 ...
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