SpringBoot学习笔记6web开发(1)

程序员文章站 2022-03-14 09:06:42

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SpringBoot学习笔记—Day05

使用spring boot:
1.) 创建springboot应用选择我们需要的模块
2.) springboot已经将我们选中的场景配置好了,只需要少量的配置就可以使用
3.) 自己编写业务代码
自动配置原理?
这个场景sprigboot帮我们配置了什么?
能不能修改?
能修改哪些配置?
能不能扩展?

xxxxAutoConfiguration //给容器中自动添加组件的类
xxxxProperties //配置类中来封装配置文件的内容的类

springboot对静态资源的映射规则
在springboot 里面,SpringMVC的配置都在WebMVCAutoConfiguration里面
WebMVCAutoConfiguration源码

		@Override  //添加资源文件映射
		public void addResourceHandlers(ResourceHandlerRegistry registry) {
			if (!this.resourceProperties.isAddMappings()) {
				logger.debug("Default resource handling disabled");
				return;
			}
			Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
			CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
			if (!registry.hasMappingForPattern("/webjars/**")) {
				customizeResourceHandlerRegistration(registry.addResourceHandler("/webjars/**")
						.addResourceLocations("classpath:/META-INF/resources/webjars/")
						.setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
			}
			String staticPathPattern = this.mvcProperties.getStaticPathPattern();
			if (!registry.hasMappingForPattern(staticPathPattern)) {
				customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern)
						.addResourceLocations(getResourceLocations(this.resourceProperties.getStaticLocations()))
						.setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
			}
		}
		
		@Bean //欢迎页映射
		public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext,
				FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
			WelcomePageHandlerMapping welcomePageHandlerMapping = new WelcomePageHandlerMapping(
					new TemplateAvailabilityProviders(applicationContext), applicationContext, getWelcomePage(),
					this.mvcProperties.getStaticPathPattern());
			welcomePageHandlerMapping.setInterceptors(getInterceptors(mvcConversionService, mvcResourceUrlProvider));
			welcomePageHandlerMapping.setCorsConfigurations(getCorsConfigurations());
			return welcomePageHandlerMapping;
		}

addResourceHandlers此方法用来添加资源文件映射
所有/webjars/**,都去classpath:/META-INF/resources/webjars/找资源
webjars,以jar包的方式引入静态资源
超链接webjars官网中可以查找到webjars的maven依赖 —webjars
SpringBoot学习笔记6web开发(1)

<!--引入jquery的webjars-->
        <dependency>
            <groupId>org.webjars.bower</groupId>
            <artifactId>jquery</artifactId>
            <version>3.2.1</version>
        </dependency>

在访问的时候,只需要访问webjars下的资源路径即可
在addResourceHandlers方法中,看到resourceProperties
ResourceProperties源码

@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false)
public class ResourceProperties {

我们可以在配置文件中设置和静态资源有关的参数,缓存时间等
在addResourceHandlers方法中,还可以看到registry.addResourceHandler(staticPathPattern),这个staticPathPattern="/**",也就是访问当前项目下的任何路径
接着看到getResourceLocations(this.resourceProperties.getStaticLocations())这行.接着查到这个getStaticLocations()方法获取到的是 { “classpath:/META-INF/resources/”,“classpath:/resources/”, “classpath:/static/”, “classpath:/public/” }数组,也就是说,这个4个路径是可以存放静态资源的,

@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false)
public class ResourceProperties {

	private static final String[] CLASSPATH_RESOURCE_LOCATIONS = { "classpath:/META-INF/resources/",
			"classpath:/resources/", "classpath:/static/", "classpath:/public/" };

如果要访问静态资源,就可以写localhost:8080/asserts/img/bootstrap-solid.svg
`` SpringBoot学习笔记6web开发(1)
welcomePageHandlerMapping方法
在WebMVCAutoConfiguration中还加入了组件welcomePageHandlerMapping的方法,作用是配置欢迎页,在welcomePageHandlerMapping方法中调用了getWelcomePage()方法,
getWelcomePage()方法源码

		private Optional<Resource> getWelcomePage() {
			String[] locations = getResourceLocations(this.resourceProperties.getStaticLocations());
			return Arrays.stream(locations).map(this::getIndexHtml).filter(this::isReadable).findFirst();
		}

		private Resource getIndexHtml(String location) {
			return this.resourceLoader.getResource(location + "index.html");
		}

可以看到getStaticLocations(),获取的还是那4个静态资源路径,后面加上index.html,接着看到mvcProperties.getStaticPathPattern()这里,获取到的是"/ * *",也就是说所有静态文件夹下的index.html都被这个"/ * *"映射
模板引擎
JSP、Velocity、Freemarker、Thymeleaf都属于模板引擎
SpringBoot学习笔记6web开发(1)
我们将后台传来的数据,与前端静态页面共同传给模板引擎,利用后台传来的数据,解析静态页面,最终组合成一个新的页面

SpringBoot推荐的Thymeleaf；语法更简单，功能更强大；
对于新版本的(我创建springboot时时用的idea推荐的2.3.1的版本),要想使用Thymeleaf模板引擎,只需要导入thymeleaf的starter即可,因为他内部设置的thymeleaf.version跟thymeleaf-layout-dialect.version都是很高的版本,如果是低版本的springboot可能还要在properties标签中重新设置这俩个标签的版本

<thymeleaf.version>3.0.11.RELEASE</thymeleaf.version>
<thymeleaf-layout-dialect.version>2.4.1</thymeleaf-layout-dialect.version>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>

Thymeleaf语法
我们找到Thymeleaf的配置文件映射类ThymeleafProperties

@ConfigurationProperties(prefix = "spring.thymeleaf")
public class ThymeleafProperties {

	private static final Charset DEFAULT_ENCODING = StandardCharsets.UTF_8; //默认字符编码

	public static final String DEFAULT_PREFIX = "classpath:/templates/"; //默认前缀

	public static final String DEFAULT_SUFFIX = ".html"; //默认后缀

	/**
	 * Whether to check that the template exists before rendering it.
	 */
	private boolean checkTemplate = true;

只要将html页面放到类路径下templates包内,thymeleaf就可以访问的到
在html内写thymeleaf时,可以先导入一个thymeleaf的名称空间,这样在写thymeleaf时,可以有语法提示

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

使用方法

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <h1>你好!</h1>
<div th:text="${hello}"></div>
</body>
</html>

语法规则
可以任意替换html标签的属性

<div id="div1" class="divClass" th:id="${hello}" th:class="${hello}" th:text="${hello}"></div>

浏览器源代码显示为:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <h1>你好!</h1>
<div id="你好" class="你好">你好</div>
</body>
</html>

与jsp比较
SpringBoot学习笔记6web开发(1)
thymeleaf的表达式语法

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: _

使用示例

@Controller
public class TestController {

    @RequestMapping("/success")
    public String success(Map<String,Object> maps){
        maps.put("hello","<h1>你好</h1>");
        maps.put("users", Arrays.asList("张三","李四","王五"));
        //默认去classpath:/templates/success.html页面
        return "success";
    }
}

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div id="div1" class="divClass" th:id="${hello}"
     th:class="${hello}" th:text="${hello}"></div>
    <div th:utext="${hello}"></div>
    <div th:text="${users[0]}"></div>
    <div th:text="${users[1]}"></div>
    <div th:text="${users[2]}"></div>
    <!--th每次遍历都会生成当前标签,一共生成3个h4标签-->
<h4 th:each="user:${users}" th:text="${user}"></h4>
<h4>
    <span th:each="user:${users}">[[${user}]]</span>
</h4>
</body>
</html>

SpringBoot学习笔记6web开发(1)

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