Spring Boot Web開發與thymeleaf模板引擎

簡介：

• 使用Springboot應用，選中須要的模塊，
• Spring已經默認將場景配置好了，只需在配置文件中少許配置就能夠運行起來
• 本身編寫業務代碼

自動配置原理

這個場景Springboot幫咱們配置了什麼、能不能修改呢？能修改哪些配置？

xxxxxAutoConfiguration ：幫咱們給容器自動配置組件

xxxproperties 配置類來封裝配置文件的內容

Springboot對靜態資源的映射規則

@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false)
public class ResourceProperties implements ResourceLoaderAware {
  //能夠設置和靜態資源有關的參數，緩存時間等

｝
 //webMVC的自動配置
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();
              //靜態資源文件夾映射
            if (!registry.hasMappingForPattern(staticPathPattern)) {
      customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern).addResourceLocations(this.resourceProperties.getStaticLocations()).setCachePeriod(cachePeriod));
            }
        }

        //配置歡迎頁映射
        @Bean
        public WelcomePageHandlerMapping welcomePageHandlerMapping(ResourceProperties resourceProperties) {
            return new WelcomePageHandlerMapping(resourceProperties.getWelcomePage(),
                    this.mvcProperties.getStaticPathPattern());
        }

       //配置喜歡的圖標 即咱們網頁標籤最左邊的圖標
        @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);
                  //全部  **/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;
            }
        }

 靜態資源的映射

• 全部的 /webjars/**  都去 classpath:/META-INF/resources/webjars/ 找資源； webjars：以jar包的方式引入靜態資源； http://www.webjars.org/

 

pom.xml 依賴：

<!--引入jquery-webjar-->在訪問的時候只須要寫webjars下面資源的名稱便可
        <dependency>
            <groupId>org.webjars</groupId>
            <artifactId>jquery</artifactId>
            <version>3.3.1</version>
        </dependency>

訪問地址：localhost:8080/webjars/jquery/3.3.1/jquery.js

• "/**" 訪問當前項目的任何資源，都去（靜態資源的文件夾）找映射

  "classpath:/META-INF/resources/", 
  "classpath:/resources/",
  "classpath:/static/", 
  "classpath:/public/" 
  "/"：當前項目的根路徑

   localhost:8080/abc === 默認去靜態資源文件夾裏面找abc

• 歡迎頁； 靜態資源文件夾下的全部index.html頁面；被"/**"映射；
  • localhost:8080/ 找index頁面 
• 全部的 **/favicon.ico 都是在靜態資源文件下找；

 模板引擎

經常使用的模板引擎有：JSP，Velocity、Freemarker、Thymeleaf

Springboot 推薦使用thymeleaf ，語法更簡單，功能更強大。

引入thymeleaf 

       <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>          
       </dependency>
SpringBoot默認的thymeleaf 版本爲 2.1.6 ，該版本過低，因此咱們須要手動切換thymeleaf版本
<properties>
        <thymeleaf.version>3.0.9.RELEASE</thymeleaf.version>
        <!-- 佈局功能的支持程序  thymeleaf3主程序  layout2以上版本 -->
        <!-- thymeleaf2   layout1-->
        <thymeleaf-layout-dialect.version>2.2.2</thymeleaf-layout-dialect.version>
  </properties>
SpringBoot 的其餘默認版本的依賴也是這樣切換，若是須要修改的話，同樣的切換思路。

配置上面這兩個的時候，啓動Springboot 會報錯誤

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

修改成如下便可：

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");

　　//只要咱們把HTML頁面放在classpath:/templates/，thymeleaf就能自動渲染；

　　public static final String DEFAULT_PREFIX = "classpath:/templates/";
   public static final String DEFAULT_SUFFIX = ".html"; 

使用：

 1，在html 頁面上導入thymeleaf的命名空間 ， 不導入也能夠，只是在寫代碼的時候，沒有相應的代碼提示。

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

thymeleaf的語法

<!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 將div裏面的文本內容設置爲 -->
    <div th:text="${hello}">這是顯示歡迎信息</div>
</body>
</html>

語法規則：

1）、th:text；改變當前元素裏面的文本內容；

　　　　th：任意html屬性；來替換原生屬性的值 

2）、表達式

Simple expressions:（表達式語法）
    Variable Expressions: ${...}：獲取變量值；OGNL；
            1）、獲取對象的屬性、調用方法
            2）、使用內置的基本對象：
                #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）、內置的一些工具對象：
#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: *{...}：選擇表達式：和${}在功能上是同樣；
        補充：配合 th:object="${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: #{...}：獲取國際化內容
    Link URL Expressions: @{...}：定義URL；
            @{/order/process(execId=${execId},execType='FAST')}
    Fragment Expressions: ~{...}：片斷引用表達式
            <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:（文本操做）
    String concatenation: +
    Literal substitutions: |The name is ${name}|
Arithmetic operations:（數學運算）
    Binary operators: + , - , * , / , %
    Minus sign (unary operator): -
Boolean operations:（布爾運算）
    Binary operators: and , or
    Boolean negation (unary operator): ! , not
Comparisons and equality:（比較運算）
    Comparators: > , < , >= , <= ( gt , lt , ge , le )
    Equality operators: == , != ( eq , ne )
Conditional operators:條件運算（三元運算符）
    If-then: (if) ? (then)
    If-then-else: (if) ? (then) : (else)
    Default: (value) ?: (defaultvalue)
Special tokens:
    No-Operation: _