Spring Boot Web开发与thymeleaf模板引擎

简介：

• 使用springboot应用，选中需要的模块，
• spring已经默认将场景配置好了，只需在配置文件中少量配置就可以运行起来
• 自己编写业务代码

自动配置原理

这个场景springboot帮我们配置了什么、能不能修改呢？能修改哪些配置？

xxxxxautoconfiguration ：帮我们给容器自动配置组件

xxxproperties 配置类来封装配置文件的内容

springboot对静态资源的映射规则

@configurationproperties(prefix = "spring.resources", ignoreunknownfields = false)
public class resourceproperties implements resourceloaderaware {
  //可以设置和静态资源有关的参数，缓存时间等

｝
 //webmvc的自动配置
webmvcauotconfiguration：
        @override
        public void addresourcehandlers(resourcehandlerregistry registry) {
            if (!this.resourceproperties.isaddmappings()) {
                logger.debug("default resource handling disabled");
                return;
            }
            integer cacheperiod = this.resourceproperties.getcacheperiod();
            if (!registry.hasmappingforpattern("/webjars/**")) {
                customizeresourcehandlerregistration(
                        registry.addresourcehandler("/webjars/**").addresourcelocations("classpath:/meta-inf/resources/webjars/").setcacheperiod(cacheperiod));
            }
            string staticpathpattern = this.mvcproperties.getstaticpathpattern();
              //静态资源文件夹映射
            if (!registry.hasmappingforpattern(staticpathpattern)) {
      customizeresourcehandlerregistration(registry.addresourcehandler(staticpathpattern).addresourcelocations(this.resourceproperties.getstaticlocations()).setcacheperiod(cacheperiod));
            }
        }

        //配置欢迎页映射
        @bean
        public welcomepagehandlermapping welcomepagehandlermapping(resourceproperties resourceproperties) {
            return new welcomepagehandlermapping(resourceproperties.getwelcomepage(),
                    this.mvcproperties.getstaticpathpattern());
        }

       //配置喜欢的图标 即我们网页标签最左边的图标
        @configuration
        @conditionalonproperty(value = "spring.mvc.favicon.enabled", matchifmissing = true)
        public static class faviconconfiguration {
            private final resourceproperties resourceproperties;
            public faviconconfiguration(resourceproperties resourceproperties) {this.resourceproperties = resourceproperties;
            }

            @bean
            public simpleurlhandlermapping faviconhandlermapping() {
                simpleurlhandlermapping mapping = new simpleurlhandlermapping();
                mapping.setorder(ordered.highest_precedence + 1);
                  //所有  **/favicon.ico 
               mapping.seturlmap(collections.singletonmap("**/favicon.ico",faviconrequesthandler()));
                return mapping;
            }

            @bean
            public resourcehttprequesthandler faviconrequesthandler() {
                resourcehttprequesthandler requesthandler = new resourcehttprequesthandler();
                requesthandler.setlocations(this.resourceproperties.getfaviconlocations());
                return requesthandler;
            }
        }

 静态资源的映射

• 所有的 /webjars/**  都去 classpath:/meta-inf/resources/webjars/ 找资源； webjars：以jar包的方式引入静态资源； /

 

pom.xml 依赖：

<!--引入jquery-webjar-->在访问的时候只需要写webjars下面资源的名称即可
        <dependency>
            <groupid>org.webjars</groupid>
            <artifactid>jquery</artifactid>
            <version>3.3.1</version>
        </dependency>

访问地址：localhost:8080/webjars/jquery/3.3.1/jquery.js

• "/**" 访问当前项目的任何资源，都去（静态资源的文件夹）找映射

  "classpath:/meta-inf/resources/", 
  "classpath:/resources/",
  "classpath:/static/", 
  "classpath:/public/" 
  "/"：当前项目的根路径

   localhost:8080/abc === 默认去静态资源文件夹里面找abc

• 欢迎页； 静态资源文件夹下的所有index.html页面；被"/**"映射；
  • localhost:8080/ 找index页面 
• 所有的 **/favicon.ico 都是在静态资源文件下找；

 模板引擎

常用的模板引擎有：jsp，velocity、freemarker、thymeleaf

springboot 推荐使用thymeleaf ，语法更简单，功能更强大。

引入thymeleaf 

       <dependency>
            <groupid>org.springframework.boot</groupid>
            <artifactid>spring-boot-starter-thymeleaf</artifactid>          
       </dependency>
springboot默认的thymeleaf 版本为 2.1.6 ，该版本太低，所以我们需要手动切换thymeleaf版本
<properties>
        <thymeleaf.version>3.0.9.release</thymeleaf.version>
        <!-- 布局功能的支持程序  thymeleaf3主程序  layout2以上版本 -->
        <!-- thymeleaf2   layout1-->
        <thymeleaf-layout-dialect.version>2.2.2</thymeleaf-layout-dialect.version>
  </properties>
springboot 的其他默认版本的依赖也是这样切换，如果需要修改的话，一样的切换思路。

配置上面这两个的时候，启动springboot 会报错误

an attempt was made to call the method org.thymeleaf.spring5.springtemplateengine.setrenderhiddenmarkersbeforecheckboxes(z)v but it does not exist. its class, org.thymeleaf.spring5.springtemplateengine, is available from the following locations:

    jar:file:/e:/springboot/repository/org/thymeleaf/thymeleaf-spring5/3.0.9.release/thymeleaf-spring5-3.0.9.release.jar!/org/thymeleaf/spring5/springtemplateengine.class

it was loaded from the following location:

    file:/e:/springboot/repository/org/thymeleaf/thymeleaf-spring5/3.0.9.release/thymeleaf-spring5-3.0.9.release.jar

action:

correct the classpath of your application so that it contains a single, compatible version of org.thymeleaf.spring5.springtemplateengine

修改为以下即可：

thymeleaf的使用

配置：

@configurationproperties(prefix = "spring.thymeleaf")
public class thymeleafproperties {
    private static final charset default_encoding = charset.forname("utf-8");
    private static final mimetype default_content_type = mimetype.valueof("text/html");

　　//只要我们把html页面放在classpath:/templates/，thymeleaf就能自动渲染；

　　public static final string default_prefix = "classpath:/templates/";
   public static final string default_suffix = ".html"; 

使用：

 1，在html 页面上导入thymeleaf的命名空间 ， 不导入也可以，只是在写代码的时候，没有相应的代码提示。

<html lang="en" xmlns:th="http://www.thymeleaf.org">

thymeleaf的语法

<!doctype html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="utf-8">
    <title>title</title>
</head>
<body>
    <h1>成功！</h1>
    <!--th:text 将div里面的文本内容设置为 -->
    <div th:text="${hello}">这是显示欢迎信息</div>
</body>
</html>

语法规则：

1）、th:text；改变当前元素里面的文本内容；

　　　　th：任意html属性；来替换原生属性的值 

2）、表达式

simple expressions:（表达式语法）
    variable expressions: ${...}：获取变量值；ognl；
            1）、获取对象的属性、调用方法
            2）、使用内置的基本对象：
                #ctx : the context object.
                #vars: the context variables.
                #locale : the context locale.
                #request : (only in web contexts) the httpservletrequest object.
                #response : (only in web contexts) the httpservletresponse object.
                #session : (only in web contexts) the httpsession object.
                #servletcontext : (only in web contexts) the servletcontext object.               
                ${session.foo}
            3）、内置的一些工具对象：
#execinfo : information about the template being processed.
#messages : methods for obtaining externalized messages inside variables expressions, in the same way as they would be obtained using #{…} syntax.
#uris : methods for escaping parts of urls/uris
#conversions : methods for executing the configured conversion service (if any).
#dates : methods for java.util.date objects: formatting, component extraction, etc.
#calendars : analogous to #dates , but for java.util.calendar objects.
#numbers : methods for formatting numeric objects.
#strings : methods for string objects: contains, startswith, prepending/appending, etc.
#objects : methods for objects in general.
#bools : methods for boolean evaluation.
#arrays : methods for arrays.
#lists : methods for lists.
#sets : methods for sets.
#maps : methods for maps.
#aggregates : methods for creating aggregates on arrays or collections.
#ids : methods for dealing with id attributes that might be repeated (for example, as a result of an iteration).

    selection variable expressions: *{...}：选择表达式：和${}在功能上是一样；
        补充：配合 th:object="${session.user}：
   <div th:object="${session.user}">
    <p>name: <span th:text="*{firstname}">sebastian</span>.</p>
    <p>surname: <span th:text="*{lastname}">pepper</span>.</p>
    <p>nationality: <span th:text="*{nationality}">saturn</span>.</p>
    </div>
    
    message expressions: #{...}：获取国际化内容
    link url expressions: @{...}：定义url；
            @{/order/process(execid=${execid},exectype='fast')}
    fragment expressions: ~{...}：片段引用表达式
            <div th:insert="~{commons :: main}">...</div>
            
literals（字面量）
      text literals: 'one text' , 'another one!' ,…
      number literals: 0 , 34 , 3.0 , 12.3 ,…
      boolean literals: true , false
      null literal: null
      literal tokens: one , sometext , main ,…
text operations:（文本操作）
    string concatenation: +
    literal substitutions: |the name is ${name}|
arithmetic operations:（数学运算）
    binary operators: + , - , * , / , %
    minus sign (unary operator): -
boolean operations:（布尔运算）
    binary operators: and , or
    boolean negation (unary operator): ! , not
comparisons and equality:（比较运算）
    comparators: > , < , >= , <= ( gt , lt , ge , le )
    equality operators: == , != ( eq , ne )
conditional operators:条件运算（三元运算符）
    if-then: (if) ? (then)
    if-then-else: (if) ? (then) : (else)
    default: (value) ?: (defaultvalue)
special tokens:
    no-operation: _