springBoot核心原理

Posted 吴二喵

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一、配置文件

yaml的写法

##map的写法1
friends: lastName: zhangsan,age: 18
##map的写法2
friends:
		lastName: zhangsan
		age: 20
###list、set写法1		
pets:
 - cat
 - dog
 - pig		
###list、set写法2
pets: [cat,dog,pig]
##单引号会将\\n作为字符串输出,双引号会将\\n作为换行输出
##双引号不会转义,单引号会转义

想要代码配置可以提示,添加如下依赖

 <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-configuration-processor</artifactId>
     <optional>true</optional>
 </dependency>

在打包的时候可以exclude相关配置

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.springframework.boot</groupId>
                            <artifactId>spring-boot-configuration-processor</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

二、Web开发

2.1 静态资源访问

1、静态资源目录
静态资源目录:类路径下如下目录

/static 
/public
/resources
/META-INF/resources

访问:当前项目根路径/+静态资源名

原理:静态映射/**
请求进来,先去controller看能不能处理,不能处理的所有请求又都交给静态资源处理器。

2、静态资源访问前缀
默认无前缀,可以在配置文件中修改
访问路径:当前项目+static-path-pattern+静态资源名=静态资源文件夹下找

spring.mvc.static-path-pattern: /res/**

修改静态资源的存放路径

spring:
  resources:
    static-location: classpath:/haha/

3、webjar
自动映射

WebJars是将web前端资源(js,css等)打成jar包文件,然后借助Maven工具,以jar包形式对web前端资源进行统一依赖管理,保证这些Web资源版本唯一性。WebJars的jar包部署在Maven中央仓库上。

访问地址:webjars/jquery/3.5.1/jquery.js

2.2 欢迎页支持

静态资源路径下 index.html
可以配置静态资源路径;但是不可以配置静态资源的访问前缀,否则导致index.html不能被默认访问。

spring.mvc.static-path-pattern: /res/**

controller能处理/index

2.3 自定义favicon

图标放在静态资源目录下即可

spring.mvc.static-path-pattern: /res/**

也会影响图标的显示

2.4 静态资源配置原理

springBoot启动默认加载xxxAutoConfiguration(自动配置类)
SpringMVC功能的自动配置类 WebMvcAutoConfiguration

@Configuration(
    proxyBeanMethods = false
)
@ConditionalOnWebApplication(
    type = Type.SERVLET
)
@ConditionalOnClass(Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class)
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(-2147483638)
@AutoConfigureAfter(DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class, ValidationAutoConfiguration.class)
public class WebMvcAutoConfiguration 
     @Configuration(
        proxyBeanMethods = false
    )
    @Import(WebMvcAutoConfiguration.EnableWebMvcConfiguration.class)
    @EnableConfigurationProperties(WebMvcProperties.class, ResourceProperties.class)
    @Order(0)
    public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer 

配置文件的相关属性和xxx进行了绑定:WebMvcProperties(spring.mvc)和ResourceProperties(spring.resources)

配置类只有一个有参构造器

//有参构造器所有参数的值都会从容器中确定
//ResourceProperties 获取和spring.resources绑定的所有值的对象
//WebMvcProperties 获取和spring.mvc绑定的所有值的对象
//ListableBeanFactory beanFactory springbean工厂
//HttpMessageConverters 找到所有的HttpMessageConverters
//resourceHandlerRegistrationCustomizer 找到资源处理器的自定义器
//ServletRegistrationBean 给应用注册sevlet,filter...
   @Import(WebMvcAutoConfiguration.EnableWebMvcConfiguration.class)
    @EnableConfigurationProperties(WebMvcProperties.class, ResourceProperties.class)
    @Order(0)
    public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer 
        private static final Log logger = LogFactory.getLog(WebMvcConfigurer.class);
        private final ResourceProperties resourceProperties;
        private final WebMvcProperties mvcProperties;
        private final ListableBeanFactory beanFactory;
        private final ObjectProvider<HttpMessageConverters> messageConvertersProvider;
        private final ObjectProvider<DispatcherServletPath> dispatcherServletPath;
        private final ObjectProvider<ServletRegistrationBean<?>> servletRegistrations;
        final WebMvcAutoConfiguration.ResourceHandlerRegistrationCustomizer resourceHandlerRegistrationCustomizer;

2、资源处理的默认规则

        public void addResourceHandlers(ResourceHandlerRegistry registry) 
            if (!this.resourceProperties.isAddMappings()) 
                logger.debug("Default resource handling disabled");
             else 
                Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
                CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
                //webjars的规则
                if (!registry.hasMappingForPattern("/webjars/**")) 
                    this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]"/webjars/**").addResourceLocations(new String[]"classpath:/META-INF/resources/webjars/").setCachePeriod(this.getSeconds(cachePeriod)).setCacheControl(cacheControl));
                

                String staticPathPattern = this.mvcProperties.getStaticPathPattern();
                if (!registry.hasMappingForPattern(staticPathPattern)) 
                    this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]staticPathPattern).addResourceLocations(WebMvcAutoConfiguration.getResourceLocations(this.resourceProperties.getStaticLocations())).setCachePeriod(this.getSeconds(cachePeriod)).setCacheControl(cacheControl));
                

            
        
##禁用所有静态资源规则
spring:
  resources:
    add-mappings: false
public class ResourceProperties 
    private static final String[] CLASSPATH_RESOURCE_LOCATIONS = new String[]"classpath:/META-INF/resources/", "classpath:/resources/", "classpath:/static/", "classpath:/public/";
    private String[] staticLocations;
    private boolean addMappings;
    private final ResourceProperties.Chain chain;
    private final ResourceProperties.Cache cache;

    public ResourceProperties() 
        this.staticLocations = CLASSPATH_RESOURCE_LOCATIONS;

3、欢迎页的处理规则

//HandlerMapping 处理器映射,保存了每个Handler能处理哪些请求
        @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;
        
    WelcomePageHandlerMapping(TemplateAvailabilityProviders templateAvailabilityProviders, ApplicationContext applicationContext, Optional<Resource> welcomePage, String staticPathPattern) 
    //要用欢迎页功能,必须是/**
        if (welcomePage.isPresent() && "/**".equals(staticPathPattern)) 
            logger.info("Adding welcome page: " + welcomePage.get());
            this.setRootViewName("forward:index.html");
         else if (this.welcomeTemplateExists(templateAvailabilityProviders, applicationContext)) 
           //调用controller /index
            logger.info("Adding welcome page template: index");
            this.setRootViewName("index");
        

    

3、请求参数处理
0、请求映射
@xxxmapping
rest风格支持:使用http请求方式动词来表示对资源的操作。
以前:/getUser,/addUser, /deleteUser,/editUser
现在:/user GE
T–请求 POST-新增 PUT–修改 DELETE–删除
核心filter:HiddenHttpMethodFilter
用法:表单method=put,隐藏域_method=put

//springboot默认不开启
   @Bean
    @ConditionalOnMissingBean(HiddenHttpMethodFilter.class)
    @ConditionalOnProperty(
        prefix = "spring.mvc.hiddenmethod.filter",
        name = "enabled",
        matchIfMissing = false
    )
<form action="/user" method="post">
	<input name="_method" type="hidden" value="delete"/>
	<input value="rest-delete提交" type="submit"/>
</form>

rest原理(表单提交使用rest)
表单提交会带上_method=put
请求过来被HiddenHttpMethodFilter
请求是否正常,并且是post
获取_method的值
兼容以下请求:delete,put,patch
原生request(post),包装模式requestWrapper重写了getMethod方法,返回的是传入的值
过滤器链放行的时候用wrapper。以后的方法调用getMethod是调用requestWrapper的。

rest使用客户端工具
如postman直接发送put,delete请求,无需filter

请求映射原理

1、httpservlet的doGet方法
2、frameworkservlet的processRequest–>doService
3、Dispatchservlet的doService实现 doDispatch(每个方法都会调用)

springmvc功能分析都从org.springframework.web.servlet.DispatcherServlet的doDispatch

    protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception 
        HttpServletRequest processedRequest = request;
        HandlerExecutionChain mappedHandler = null;
        boolean multipartRequestParsed = false;
        WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

        try 
            try 
                ModelAndView mv = null;
                Object dispatchException = null;

                try 
                    processedRequest = this.checkMultipart(request);
                    multipartRequestParsed = processedRequest != request;
                    //找到当前请求使用哪个handler(controller)处理
                    mappedHandler = this.getHandler(processedRequest);
                    if (mappedHandler == null) 
                        this.noHandlerFound(processedRequest, response);
                        return;
                    

所有的请求映射都保存在HandlerMapping(处理器映射)中
	1、springBoot自动配置欢迎页的WelcomePageHandlerMapping,访问/会访问到index.html
	2、RequestMappingHandlerMapping:保存了所有@RequestMapping和handler的映射规则,springBoot自动配置
	3、请求进来挨个尝试所有的handlerMapping看是否有请求信息
	4、我们也可以自定义handlerMapping

一、普通参数与基本注解
1、注解

@PathVariable 路径变量
@RequestParam 请求参数
@RequestHeader 请求头
@CookieValue cookie值
@RequestAttribute request域属性
@RequestBody 请求体
@MatrixVariable 矩阵变量

 @GetMapping("/car/id/owner/username")
    public Map<String ,Object> getCar(@PathVariable("id") Integer id,
                                      @PathVariable("username") String name,
                                      @PathVariable Map<String,String> pv,
                                      @RequestHeader("user-Agent") String userAgent,
                                      @RequestHeader Map<String, String> header,
                                      @RequestParam("age") Integer age,
                                      @RequestParam("inters") List<String> inters,
                                      @RequestParam Map<String, String> params,
                                      @CookieValue("_ga") String _ga,
                                      @CookieValue Cookie cookie)
                                      
    @PostMapping("/save")
    public Map post(@RequestBody String content)

@Controller
public class RequestController 

    @GetMapping("/goto")
    public String gotoPage(HttpServletRequest request)
        request.setAttribute("msg","成功了。。");
        return "forward:/success";//转发到/success请求
    

    @ResponseBody
    @GetMapping("/success")
    public Map success(@RequestAttribute("msg") String msg,
                       HttpServletRequest request)
        Map<String, Object> map = new HashMap<>();
        map.put("annotation_msg",msg);
        map.put("reqMethod_msg",msg);
        return map;
    


/cars/path?aaa=bbb&ccc=ddd queryString查询字符串 @RequestParam
/cars/path;low=24;brand=byd,audi 矩阵变量
页面开发的时候,如果cookie被禁用了,session里面的内容怎么使用
session.set(a,b)---->jsessionid---->cookie----->每次请求都携带
url重写的方式:/adc;jseesionid=xxx 把cookie的值使用矩阵变量的方式进行传递
如/cars/sell;low=34;brand=byd,audi
springBoot默认禁用了矩阵变量的功能
手动开启的原理:对于路径的处理,urlPathHelper进行解析,setRemoveSemicolonContent设置false来支持矩阵变量
矩阵变量必须有url路径变量才能被解析
  @GetMapping("/boss/bossId/empId")
    public Map boss(@MatrixVariable(value = "age", pathVar = "bossId") Integer bossAge,
                @MatrixVariable(value = "age", pathVar = "empId") Integer empAge)

参数处理的原理
1、HandlerMapping中找到处理请求的Handler(Controller.method())
2、为当前Handler找一个适配器 HandlerAdapter
RequestMappingHandlerAdapter–支持方法上标注@RequestMapping的
HandlerFunctionAdapter–支持函数式编程的

//DispatchServlet中的doDispatch方法中
                    mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

//RequestMappingHandlerAdapter的handleInternal方法中
//执行目标方法
            mav = this.invokeHandlerMethod(request, response, handlerMethod);

ServletInvocableHandlerMethod
        Object returnValue = this.invokeForRequest(webRequest, mavContainer, providedArgs);

//InvocableHandlerMethod
//5、如何确定目标方法的每个参数值
protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
			Object... providedArgs) throws Exception 

		MethodParameter[] parameters = getMethodParameters();
		if (ObjectUtils.isEmpty(parameters)) 
			return EMPTY_ARGS;
		

		Object[] args = new Object[parameters.length];
		for (int i = 0; i < parameters.length; i++) 
			MethodParameter parameter = parameters[i];
			parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);
			args[i] = findProvidedArgument(parameter, providedArgs);
			if (args[i] != null) 
				continue;
			
			if (!this.resolvers.supportsParameter(parameter)) 
				throw new IllegalStateException(formatArgumentError(parameter, "No suitable resolver"));
			
			try 
				args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);
			
			catch (Exception ex) 
				// Leave stack trace for later, exception may actually be resolved and handled...
				if (logger.isDebugEnabled()) 
					String exMsg = ex.getMessage();
					if (exMsg != null && !exMsg.contains(parameter.getExecutable().toGenericString())) 《02.Spring Boot连载:Spring Boot实战.Spring Boot核心原理剖析》

程序员必备技能之SpringBoot的自动装配原理,很详细,建议收藏!!!

程序员必备技能之SpringBoot的自动装配原理,很详细,建议收藏!!!

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