4, Web development

1, introduction

Use SpringBoot;

1) . create a spring boot application and select the modules we need;

2) Spring boot has configured these scenarios by default. You only need to specify a few configurations in the configuration file to run them

3) . write your own business code;

Principle of automatic configuration?

What does spring boot help us to configure for this scenario? Can you modify it? What configurations can be modified? Can we expand it? xxx

xxxxAutoConfiguration: help us to automatically configure components in the container;
xxxxProperties: configuration class to encapsulate the content of configuration file;

2. Spring boot's mapping rules for static resources;

@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false)
public class ResourceProperties implements ResourceLoaderAware {
  //You can set parameters related to static resources, cache time, etc

	WebMvcAutoConfiguration: 
		@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();
          	//Static resource folder mapping
			if (!registry.hasMappingForPattern(staticPathPattern)) {
				customizeResourceHandlerRegistration(
						registry.addResourceHandler(staticPathPattern)
								.addResourceLocations(
										this.resourceProperties.getStaticLocations())
						.setCachePeriod(cachePeriod));
			}
		}

        //Configure welcome page mapping
		@Bean
		public WelcomePageHandlerMapping welcomePageHandlerMapping(
				ResourceProperties resourceProperties) {
			return new WelcomePageHandlerMapping(resourceProperties.getWelcomePage(),
					this.mvcProperties.getStaticPathPattern());
		}

       //Configure favorite icons
		@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);
              	//All  **/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;
			}

		}

1) , all / webjars / * *, go to classpath:/META-INF/resources/webjars / to find resources;
webjars: static resources are introduced by jar package;

http://www.webjars.org/

localhost:8080/webjars/jquery/3.3.1/jquery.js

<! -- introduce jQuery webjar -- > when accessing, you only need to write the name of the resource under webjars
		<dependency>
			<groupId>org.webjars</groupId>
			<artifactId>jquery</artifactId>
			<version>3.3.1</version>
		</dependency>

2) "/ * *" to access any resources of the current project, go to (the folder of static resources) to find the mapping

"classpath:/META-INF/resources/", 
"classpath:/resources/",
"classpath:/static/", 
"classpath:/public/" 
'/': the root path of the current project

localhost:8080/abc = = = go to the static resource folder to find abc

3) , welcome page; all index.html pages under the static resource folder; mapped by "/ * *;

localhost:8080 / find the index page

4) , all * * / favicon.ico s are found under the static resource file;

3. Template engine

JSP,Velocity,Freemarker,Thymeleaf

Thymeleaf recommended by SpringBoot;

The grammar is simpler and more powerful;

1. Introducing thymeleaf;

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-thymeleaf</artifactId>
          	2.1.6
		</dependency>
//Switch thymeleaf version
<properties>
		<thymeleaf.version>3.0.9.RELEASE</thymeleaf.version>
		<!-- Support program for layout function  thymeleaf3 main program  layout2 Above version -->
		<!-- thymeleaf2   layout1-->
		<thymeleaf-layout-dialect.version>2.2.2</thymeleaf-layout-dialect.version>
  </properties>

2. Use of Thymeleaf

@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");

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

	public static final String DEFAULT_SUFFIX = ".html";
  	//

As long as we put the HTML page in classpath:/templates /, thmeleaf can render automatically;

Use:

1. Import namespace of thymeleaf

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

2. Using thmeleaf syntax;

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <h1>Success!</h1>
    <!--th:text take div The text content is set as -->
    <div th:text="${hello}">This is a welcome message</div>
</body>
</html>

3. Grammatical rules

1) , th:text; change the text content in the current element;

th: any html attribute; to replace the value of the native attribute

2) , expression?

Simple expressions:(Expression syntax)
    Variable Expressions: ${...}: Get the variable value; OGNL；
    		1),Get object properties, call methods
    		2),Use built-in base objects:
    			#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),Some built-in tool objects:
#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: *{...}: Select expressions: and ${}It is the same in function;
    	//Add: with th:object="${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: #{...}: get international content
    Link URL Expressions: @{...}: Definition URL；
    		@{/order/process(execId=${execId},execType='FAST')}
    Fragment Expressions: ~{...}: Fragment reference expression
    		<div th:insert="~{commons :: main}">...</div>
    		
Literals(Literal)
      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:(Text operation)
    String concatenation: +
    Literal substitutions: |The name is ${name}|
Arithmetic operations:(Mathematical operation)
    Binary operators: + , - , * , / , %
    Minus sign (unary operator): -
Boolean operations:(Boolean operation)
    Binary operators: and , or
    Boolean negation (unary operator): ! , not
Comparisons and equality:(Comparison operation)
    Comparators: > , < , >= , <= ( gt , lt , ge , le )
    Equality operators: == , != ( eq , ne )
Conditional operators:Conditional operation (ternary operator)
    If-then: (if) ? (then)
    If-then-else: (if) ? (then) : (else)
    Default: (value) ?: (defaultvalue)
Special tokens:
    No-Operation: _