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        Tagcontrollers    package:com.grailsinactin        PostController        ProfileController        UserController        TagControllerviews    layout        main.gsp    user        advResults.gsp        advSearch.gsp        results.gsp        search.gst    error.gsptest/integration    package:com.grailsinaction        PostIntegrationTests        UserIntegrationTests        QueryIntegrationTestsweb-app    css        hubbub.css    images        backgroud.png        headerlogo.png

6、代码打包下载