四、Web開發 1
四、Web開發
1、簡介
使用SpringBoot;
1)、建立SpringBoot應用,選中我們需要的模組;
2)、SpringBoot已經預設將這些場景配置好了,只需要在配置檔案中指定少量配置就可以執行起來
3)、自己編寫業務程式碼;
自動配置原理?
這個場景SpringBoot幫我們配置了什麼?能不能修改?能修改哪些配置?能不能擴充套件?xxx
xxxxAutoConfiguration:幫我們給容器中自動配置元件;
xxxxProperties:配置類來封裝配置檔案的內容;
2、SpringBoot對靜態資源的對映規則;
@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false) public class ResourceProperties implements ResourceLoaderAware { //可以設定和靜態資源有關的引數,快取時間等
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(); //靜態資原始檔夾對映 if (!registry.hasMappingForPattern(staticPathPattern)) { customizeResourceHandlerRegistration( registry.addResourceHandler(staticPathPattern) .addResourceLocations( this.resourceProperties.getStaticLocations()) .setCachePeriod(cachePeriod)); } } //配置歡迎頁對映 @Bean public WelcomePageHandlerMapping welcomePageHandlerMapping( ResourceProperties resourceProperties) { return new WelcomePageHandlerMapping(resourceProperties.getWelcomePage(), this.mvcProperties.getStaticPathPattern()); } //配置喜歡的圖示 @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; } }
1)、所有 /webjars/** ,都去 classpath:/META-INF/resources/webjars/ 找資源;
webjars:以jar包的方式引入靜態資源;
localhost:8080/webjars/jquery/3.3.1/jquery.js
<!--引入jquery-webjar-->在訪問的時候只需要寫webjars下面資源的名稱即可 <dependency> <groupId>org.webjars</groupId> <artifactId>jquery</artifactId> <version>3.3.1</version> </dependency>
2)、"/**" 訪問當前專案的任何資源,都去(靜態資源的資料夾)找對映
"classpath:/META-INF/resources/",
"classpath:/resources/",
"classpath:/static/",
"classpath:/public/"
"/":當前專案的根路徑
localhost:8080/abc === 去靜態資原始檔夾裡面找abc
3)、歡迎頁; 靜態資原始檔夾下的所有index.html頁面;被"/**"對映;
localhost:8080/ 找index頁面
4)、所有的 **/favicon.ico 都是在靜態資原始檔下找;
3、模板引擎
JSP、Velocity、Freemarker、Thymeleaf
SpringBoot推薦的Thymeleaf;
語法更簡單,功能更強大;
1、引入thymeleaf;
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
2.1.6
</dependency>
切換thymeleaf版本
<properties>
<thymeleaf.version>3.0.9.RELEASE</thymeleaf.version>
<!-- 佈局功能的支援程式 thymeleaf3主程式 layout2以上版本 -->
<!-- thymeleaf2 layout1-->
<thymeleaf-layout-dialect.version>2.2.2</thymeleaf-layout-dialect.version>
</properties>
2、Thymeleaf使用
@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";
//
只要我們把HTML頁面放在classpath:/templates/,thymeleaf就能自動渲染;
使用:
1、匯入thymeleaf的名稱空間
<html lang="en" xmlns:th="http://www.thymeleaf.org">
2、使用thymeleaf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裡面的文字內容設定為 -->
<div th:text="${hello}">這是顯示歡迎資訊</div>
</body>
</html>
3、語法規則
1)、th:text;改變當前元素裡面的文字內容;
th:任意html屬性;來替換原生屬性的值
2)、表示式?
Simple expressions:(表示式語法)
Variable Expressions: ${...}:獲取變數值;OGNL;
1)、獲取物件的屬性、呼叫方法
2)、使用內建的基本物件:
#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.
${session.foo}
3)、內建的一些工具物件:
#execInfo : information about the template being processed.
#messages : methods for obtaining externalized messages inside variables expressions, in the same way as they would be obtained using #{…} syntax.
#uris : methods for escaping parts of URLs/URIs
#conversions : methods for executing the configured conversion service (if any).
#dates : methods for java.util.Date objects: formatting, component extraction, etc.
#calendars : analogous to #dates , but for java.util.Calendar objects.
#numbers : methods for formatting numeric objects.
#strings : methods for String objects: contains, startsWith, prepending/appending, etc.
#objects : methods for objects in general.
#bools : methods for boolean evaluation.
#arrays : methods for arrays.
#lists : methods for lists.
#sets : methods for sets.
#maps : methods for maps.
#aggregates : methods for creating aggregates on arrays or collections.
#ids : methods for dealing with id attributes that might be repeated (for example, as a result of an iteration).
Selection Variable Expressions: *{...}:選擇表示式:和${}在功能上是一樣;
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: ~{...}:片段引用表示式
<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:(文字操作)
String concatenation: +
Literal substitutions: |The name is ${name}|
Arithmetic operations:(數學運算)
Binary operators: + , - , * , / , %
Minus sign (unary operator): -
Boolean operations:(布林運算)
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(三元運算子)
If-then: (if) ? (then)
If-then-else: (if) ? (then) : (else)
Default: (value) ?: (defaultvalue)
Special tokens:
No-Operation: _
4、SpringMVC自動配置
1. Spring MVC auto-configuration
Spring Boot 自動配置好了SpringMVC
以下是SpringBoot對SpringMVC的預設配置:(WebMvcAutoConfiguration)
-
Inclusion of
ContentNegotiatingViewResolver
andBeanNameViewResolver
beans.- 自動配置了ViewResolver(檢視解析器:根據方法的返回值得到檢視物件(View),檢視物件決定如何渲染(轉發?重定向?))
- ContentNegotiatingViewResolver:組合所有的檢視解析器的;
- 如何定製:我們可以自己給容器中新增一個檢視解析器;自動的將其組合進來;
-
Support for serving static resources, including support for WebJars (see below).靜態資原始檔夾路徑,webjars
-
Static
index.html
support. 靜態首頁訪問 -
Custom
Favicon
support (see below). favicon.ico
-
自動註冊了 of
Converter
,GenericConverter
,Formatter
beans.- Converter:轉換器; public String hello(User user):型別轉換使用Converter
Formatter
格式化器; 2017.12.17===Date;
@Bean
@ConditionalOnProperty(prefix = "spring.mvc", name = "date-format")//在檔案中配置日期格式化的規則
public Formatter<Date> dateFormatter() {
return new DateFormatter(this.mvcProperties.getDateFormat());//日期格式化元件
}
自己新增的格式化器轉換器,我們只需要放在容器中即可
-
Support for
HttpMessageConverters
(see below).-
HttpMessageConverter:SpringMVC用來轉換Http請求和響應的;User---Json;
-
HttpMessageConverters
是從容器中確定;獲取所有的HttpMessageConverter;自己給容器中新增HttpMessageConverter,只需要將自己的元件註冊容器中(@Bean,@Component)
-
-
Automatic registration of
MessageCodesResolver
(see below).定義錯誤程式碼生成規則 -
Automatic use of a
ConfigurableWebBindingInitializer
bean (see below).我們可以配置一個ConfigurableWebBindingInitializer來替換預設的;(新增到容器)
初始化WebDataBinder; 請求資料=====JavaBean;
org.springframework.boot.autoconfigure.web:web的所有自動場景;
If you want to keep Spring Boot MVC features, and you just want to add additional MVC configuration (interceptors, formatters, view controllers etc.) you can add your own @Configuration
class of type WebMvcConfigurerAdapter
, but without @EnableWebMvc
. If you wish to provide custom instances of RequestMappingHandlerMapping
, RequestMappingHandlerAdapter
or ExceptionHandlerExceptionResolver
you can declare a WebMvcRegistrationsAdapter
instance providing such components.
If you want to take complete control of Spring MVC, you can add your own @Configuration
annotated with @EnableWebMvc
.
2、擴充套件SpringMVC
<mvc:view-controller path="/hello" view-name="success"/>
<mvc:interceptors>
<mvc:interceptor>
<mvc:mapping path="/hello"/>
<bean></bean>
</mvc:interceptor>
</mvc:interceptors>
編寫一個配置類(@Configuration),是WebMvcConfigurerAdapter型別;不能標註@EnableWebMvc;
既保留了所有的自動配置,也能用我們擴充套件的配置;
//使用WebMvcConfigurerAdapter可以來擴充套件SpringMVC的功能
@Configuration
public class MyMvcConfig extends WebMvcConfigurerAdapter {
@Override
public void addViewControllers(ViewControllerRegistry registry) {
// super.addViewControllers(registry);
//瀏覽器傳送 /atguigu 請求來到 success
registry.addViewController("/atguigu").setViewName("success");
}
}
原理:
1)、WebMvcAutoConfiguration是SpringMVC的自動配置類
2)、在做其他自動配置時會匯入;@Import(EnableWebMvcConfiguration.class)
@Configuration
public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration {
private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();
//從容器中獲取所有的WebMvcConfigurer
@Autowired(required = false)
public void setConfigurers(List<WebMvcConfigurer> configurers) {
if (!CollectionUtils.isEmpty(configurers)) {
this.configurers.addWebMvcConfigurers(configurers);
//一個參考實現;將所有的WebMvcConfigurer相關配置都來一起呼叫;
@Override
// public void addViewControllers(ViewControllerRegistry registry) {
// for (WebMvcConfigurer delegate : this.delegates) {
// delegate.addViewControllers(registry);
// }
}
}
}
3)、容器中所有的WebMvcConfigurer都會一起起作用;
4)、我們的配置類也會被呼叫;
效果:SpringMVC的自動配置和我們的擴充套件配置都會起作用;
3、全面接管SpringMVC;
SpringBoot對SpringMVC的自動配置不需要了,所有都是我們自己配置;所有的SpringMVC的自動配置都失效了
我們需要在配置類中新增@EnableWebMvc即可;
//使用WebMvcConfigurerAdapter可以來擴充套件SpringMVC的功能
@EnableWebMvc
@Configuration
public class MyMvcConfig extends WebMvcConfigurerAdapter {
@Override
public void addViewControllers(ViewControllerRegistry registry) {
// super.addViewControllers(registry);
//瀏覽器傳送 /atguigu 請求來到 success
registry.addViewController("/atguigu").setViewName("success");
}
}
原理:
為什麼@EnableWebMvc自動配置就失效了;
1)@EnableWebMvc的核心
@Import(DelegatingWebMvcConfiguration.class)
public @interface EnableWebMvc {
2)、
@Configuration
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {
3)、
@Configuration
@ConditionalOnWebApplication
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class,
WebMvcConfigurerAdapter.class })
//容器中沒有這個元件的時候,這個自動配置類才生效
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class,
ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {
4)、@EnableWebMvc將WebMvcConfigurationSupport元件匯入進來;
5)、匯入的WebMvcConfigurationSupport只是SpringMVC最基本的功能;
5、如何修改SpringBoot的預設配置
模式:
1)、SpringBoot在自動配置很多元件的時候,先看容器中有沒有使用者自己配置的(@Bean、@Component)如果有就用使用者配置的,如果沒有,才自動配置;如果有些元件可以有多個(ViewResolver)將使用者配置的和自己預設的組合起來;
2)、在SpringBoot中會有非常多的xxxConfigurer幫助我們進行擴充套件配置
3)、在SpringBoot中會有很多的xxxCustomizer幫助我們進行定製配置