首先來(lái)解釋一下SpringBoot首頁(yè)設(shè)置的三種方式
1.SpringBoot默認(rèn)首頁(yè)設(shè)置
編寫(xiě)一個(gè)最簡(jiǎn)單的html文件 index.html
!DOCTYPE html>
html lang="en">
head>
meta charset="UTF-8">
/head>
body>
h1>首頁(yè)/h1>
/body>
/html>
將index.html文件置于SpringBoot的任一靜態(tài)資源目錄下
http://localhost:8080/訪問(wèn)，成功顯示
源碼分析
首先找對(duì)應(yīng)的自動(dòng)配置類WebMvcAutoConfiguration中的對(duì)應(yīng)代碼
@Bean
public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext, FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
WelcomePageHandlerMapping welcomePageHandlerMapping =
new WelcomePageHandlerMapping(new TemplateAvailabilityProviders(applicationContext),
applicationContext, this.getWelcomePage(), this.mvcProperties.getStaticPathPattern());
welcomePageHandlerMapping.setInterceptors(this.getInterceptors(mvcConversionService, mvcResourceUrlProvider));
welcomePageHandlerMapping.setCorsConfigurations(this.getCorsConfigurations());
return welcomePageHandlerMapping;
}
可以看到 SpringBoot注冊(cè)了WelcomePageHandlerMappingBean來(lái)處理項(xiàng)目的默認(rèn)首頁(yè),構(gòu)造器中的this.getWelcomePage()為首頁(yè)資源。
private Resource getWelcomePage() {
String[] var1 = this.resourceProperties.getStaticLocations();
int var2 = var1.length;
for(int var3 = 0; var3 var2; ++var3) {
String location = var1[var3];
Resource indexHtml = this.getIndexHtml(location);
if (indexHtml != null) {
return indexHtml;
}
}
ServletContext servletContext = this.getServletContext();
if (servletContext != null) {
return this.getIndexHtml((Resource)(new ServletContextResource(servletContext, "/")));
} else {
return null;
}
}
分析這段代碼，首先獲取了this.resourceProperties的StaticLocations字段，顧名思義就是靜態(tài)路徑，那就先跟蹤StaticLocations
可以看出StaticLocations是WebPropertis中內(nèi)部靜態(tài)類Resources的屬性，從構(gòu)造器中可以看出它的值為
private static final String[] CLASSPATH_RESOURCE_LOCATIONS = new String[]{"classpath:/META-INF/resources/", "classpath:/resources/", "classpath:/static/", "classpath:/public/"};
顯而易見(jiàn)，這其實(shí)就是SpringBoot的靜態(tài)資源目錄
/META-INF
/resources/
/resources/
/static/
/public/
回到之前的代碼，獲取了StaticLocations后，通過(guò)循環(huán)遍歷，很明顯可以看到一個(gè)新的方法this.getIndexHtml(location)
private Resource getIndexHtml(String location) {
return this.getIndexHtml(this.resourceLoader.getResource(location));
}
使用this.resourceLoader返回一個(gè)與location對(duì)應(yīng)的Resource執(zhí)行另一個(gè)getIndexHtml()函數(shù)
private Resource getIndexHtml(Resource location) {
try {
Resource resource = location.createRelative("index.html");
if (resource.exists() resource.getURL() != null) {
return resource;
}
} catch (Exception var3) {
}
return null;
}
很明顯，這個(gè)方法是獲取對(duì)應(yīng)目錄下的index.html文件。再往回看
for(int var3 = 0; var3 var2; ++var3) {
String location = var1[var3];
Resource indexHtml = this.getIndexHtml(location);
if (indexHtml != null) {
return indexHtml;
}
}
當(dāng)找到對(duì)應(yīng)文件的時(shí)候就返回對(duì)應(yīng)的資源，這就是SpringBoot設(shè)置首頁(yè)的默認(rèn)方式的原理。
從源碼中也可以看出另一個(gè)關(guān)于靜態(tài)資源目錄優(yōu)先級(jí)的問(wèn)題。getWelcomePage遍歷靜態(tài)資源目錄，一旦找到就返回，所以優(yōu)先級(jí)和staticLocations中的順序相對(duì)，驗(yàn)證一下。
先在每一個(gè)目錄下建立對(duì)應(yīng)的indx.html文件
http://localhost:8080/訪問(wèn)
和得出的結(jié)論一樣，優(yōu)先級(jí)最高的是 /META-INF/resources/，把 /META-INF/resources/下的index.html文件刪除再次驗(yàn)證
驗(yàn)證成功！
2.controller里添加"/"的映射路徑
新建IndexController.java
package com.springboot04webapp.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
public class IndexController {
@RequestMapping("/")
public String index(){
return "indexController";
}
}
首頁(yè)資源indexController.html
!DOCTYPE html>
html lang="en">
head>
meta charset="UTF-8">
/head>
body>
h1>indexController首頁(yè)/h1>
/body>
/html>
http://localhost:8080/訪問(wèn)
3.MVC擴(kuò)展配置實(shí)現(xiàn)
新建MyMvcConfiguration配置類，擴(kuò)展MVC配置，重寫(xiě)addViewControllers方法
package com.springboot04webapp.config;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
@Configuration
public class MyMvcConfiguration implements WebMvcConfigurer {
@Override
public void addViewControllers(ViewControllerRegistry registry) {
registry.addViewController("/").setViewName("indexMVC");
}
}
首頁(yè)資源indexMVC.html
!DOCTYPE html>
html lang="en">
head>
meta charset="UTF-8">
/head>
body>
h1>indexMVC首頁(yè)/h1>
/body>
/html>
http://localhost:8080/訪問(wèn)
擴(kuò)展：優(yōu)先級(jí)問(wèn)題
之前的三個(gè)方法都是單獨(dú)設(shè)置的，現(xiàn)在把他們結(jié)合起來(lái)
http://localhost:8080/訪問(wèn)
優(yōu)先級(jí)最高的是第二種方法，然后將indexController刪除，再次驗(yàn)證
得出結(jié)論：Controller>MyMvcConfiguration>默認(rèn)方法
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