Spring Boot Web开发与thymeleaf模板引擎

太过爱你忘了你带给我的痛 2021-11-09 07:54 310阅读 0赞

## 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  默认识别我们template下的index.html; 页面
            @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； [http://www.webjars.org][http_www.webjars.org]/

![1479786-20190703220326554-1063756840.png][]

pom.xml 依赖：

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 （以下路径优先级从上往下）**
    
        "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

![1479786-20190703223922890-1617754040.png][]

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>
            
            
            <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。

### ![1479786-20190704000319971-78776384.png][] ###

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：  
![1479786-20190704000616006-2059752401.png][]

### 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。

### 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>
        
        <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

![1479786-20190703231738902-418595643.png][]

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: _

转载于:https://www.cnblogs.com/thelovelybugfly/p/11123629.html

[http_www.webjars.org]: http://www.webjars.org
[1479786-20190703220326554-1063756840.png]: /images/20211109/09677b39481e4f55bf0092036c11757d.png
[1479786-20190703223922890-1617754040.png]: /images/20211109/b6b8b0e873d9454fa46dc754e4603d43.png
[1479786-20190704000319971-78776384.png]: /images/20211109/8521b559ee5945acbf4cc4e98dcb38dd.png
[1479786-20190704000616006-2059752401.png]: /images/20211109/465dd5e2788b429f9cb44c62443922ac.png
[1479786-20190703231738902-418595643.png]: /images/20211109/8eac7a4f1ed743c9b3ff96bae2e2c1fd.png