Merge branch 'master' of github.com:heibaiying/Spring-All-In-One

2018-12-19 17:48:32 +08:00
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+# springmvc基础（基于注解）
+
+**开发环境：IDEA**
+
+**spring版本：5.1.3.RELEASE**
+
+**本部分内容官方文档链接：[Web Servlet](https://docs.spring.io/spring/docs/5.1.3.RELEASE/spring-framework-reference/web.html#spring-web)**
+
+## 一、搭建hello spring工程
+
+### 1.1 项目搭建
+
+1.新建maven web工程，并引入相应的依赖
+
+```xml
+ <properties>
+        <spring-base-version>5.1.3.RELEASE</spring-base-version>
+ </properties>
+
+<dependencies>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-context</artifactId>
+            <version>${spring-base-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-beans</artifactId>
+            <version>${spring-base-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-core</artifactId>
+            <version>${spring-base-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-web</artifactId>
+            <version>${spring-base-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-webmvc</artifactId>
+            <version>${spring-base-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>javax.servlet</groupId>
+            <artifactId>javax.servlet-api</artifactId>
+            <version>4.0.1</version>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
+```
+
+2.得益于servlet3.0和spring的支持，我们可以在没有web.xml的情况下完成关于servlet配置。
+
+   新建DispatcherServletInitializer.java文件,这个类的作用相当于我们在xml方式下web.xml中配置的DispatcherServlet
+
+```java
+package com.heibaiying.config;
+
+import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
+
+/**
+ * @author : heibaiying
+ */
+
+public class DispatcherServletInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
+
+    protected Class<?>[] getRootConfigClasses() {
+        return new Class[0];
+    }
+
+    protected Class<?>[] getServletConfigClasses() {
+        return new Class[]{ServletConfig.class};
+    }
+
+    protected String[] getServletMappings() {
+        return new String[]{"/"};
+    }
+}
+
+```
+
+3.新建ServletConfig.java，文件内容如下(这个类相当于我们在xml配置方式中的springApplication.xml)
+
+```java
+package com.heibaiying.config;
+
+import com.heibaiying.exception.NoAuthExceptionResolver;
+import com.heibaiying.interceptors.MyFirstInterceptor;
+import com.heibaiying.interceptors.MySecondInterceptor;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.servlet.HandlerExceptionResolver;
+import org.springframework.web.servlet.ViewResolver;
+import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
+import org.springframework.web.servlet.config.annotation.EnableWebMvc;
+import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+import org.springframework.web.servlet.view.InternalResourceViewResolver;
+
+import java.util.List;
+
+/**
+ * @author : heibaiying
+ */
+@Configuration
+@EnableWebMvc
+@ComponentScan(basePackages = {"com.heibaiying.controller"})
+public class ServletConfig implements WebMvcConfigurer {
+
+    /**
+     * 配置视图解析器
+     */
+    @Bean
+    public ViewResolver viewResolver() {
+        InternalResourceViewResolver internalResourceViewResolver = new InternalResourceViewResolver();
+        internalResourceViewResolver.setPrefix("/WEB-INF/jsp/");
+        internalResourceViewResolver.setSuffix(".jsp");
+        internalResourceViewResolver.setExposeContextBeansAsAttributes(true);
+        return internalResourceViewResolver;
+    }
+
+    /**
+     * 配置静态资源处理器
+     */
+    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
+        configurer.enable();
+    }
+
+}
+
+```
+
+4.在src 下新建controller用于测试
+
+```java
+package com.heibaiying.controller;
+
+import com.heibaiying.exception.NoAuthException;
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.RequestMapping;
+
+/**
+ * @author : heibaiying
+ * @description : hello spring
+ */
+
+@Controller
+@RequestMapping("mvc")
+public class HelloController {
+
+    @RequestMapping("hello")
+    private String hello() {
+        return "hello";
+    }
+
+}
+
+```
+
+5.在WEB-INF 下新建jsp文件夹，新建hello.jsp 文件
+
+```jsp
+<%@ page contentType="text/html;charset=UTF-8" language="java" %>
+<html>
+<head>
+    <title>Title</title>
+</head>
+<body>
+    Hello Spring MVC!
+</body>
+</html>
+```
+
+6.启动tomcat服务，访问localhost:8080/mvc/hello
+
+### 1.2 相关注解说明
+
+**1.@Configuration**
+
+@Configuration用于定义配置类，可替换xml配置文件，被注解的类内部包含有一个或多个被@Bean注解的方法，这些方法将会被AnnotationConfigApplicationContext或AnnotationConfigWebApplicationContext类进行扫描，并用于构建bean定义，初始化Spring容器。
+
+**2.@EnableWebMvc**
+
+简单的说就是提供了部分springmvc的功能，例如格式转换和参数绑定。
+
+
+
+## 二、配置自定义拦截器
+
+1.创建自定义拦截器，实现接口HandlerInterceptor（这里我们创建两个拦截器，用于测试拦截器方法的执行顺序）
+
+```java
+package com.heibaiying.interceptors;
+
+import org.springframework.web.servlet.HandlerInterceptor;
+import org.springframework.web.servlet.ModelAndView;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+/**
+ * @author : heibaiying
+ * @description : spring5 中 preHandle，postHandle，afterCompletion 在接口中被声明为默认方法
+ */
+public class MyFirstInterceptor implements HandlerInterceptor {
+
+    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
+        System.out.println("进入第一个拦截器preHandle");
+        return true;
+    }
+
+    // 需要注意的是，如果对应的程序报错，不一定会进入这个方法 但一定会进入afterCompletion这个方法
+    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) {
+        System.out.println("进入第一个拦截器postHandle");
+    }
+
+    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
+        System.out.println("进入第一个拦截器afterCompletion");
+    }
+}
+```
+
+```java
+package com.heibaiying.interceptors;
+
+import org.springframework.web.servlet.HandlerInterceptor;
+import org.springframework.web.servlet.ModelAndView;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+/**
+ * @author : heibaiying
+ * @description : spring5 中 preHandle，postHandle，afterCompletion 在接口中被声明为默认方法
+ */
+public class MySecondInterceptor implements HandlerInterceptor {
+
+    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
+        System.out.println("进入第二个拦截器preHandle");
+        return true;
+    }
+
+    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) {
+        System.out.println("进入第二个拦截器postHandle");
+    }
+
+    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
+        System.out.println("进入第二个拦截器afterCompletion");
+    }
+}
+
+```
+
+2.在ServletConfig.java中注册自定义拦截器
+
+```java
+ /**
+  * 添加自定义拦截器
+  */
+    public void addInterceptors(InterceptorRegistry registry) {
+        registry.addInterceptor(new MyFirstInterceptor()).addPathPatterns("/mvc/**").excludePathPatterns("mvc/login");
+        registry.addInterceptor(new MySecondInterceptor()).addPathPatterns("/mvc/**");
+    }
+```
+
+3.关于多个拦截器方法执行顺序的说明
+
+拦截器的执行顺序是按声明的先后顺序执行的，先声明的拦截器中的preHandle方法会先执行，然而它的postHandle方法和afterCompletion方法却会后执行。
+
+
+
+## 三、全局异常处理 
+
+1.定义自定义异常
+
+```java
+package com.heibaiying.exception;
+
+/**
+ * @author : heibaiying
+ * @description : 自定义无权限异常
+ */
+public class NoAuthException extends RuntimeException {
+
+    public NoAuthException() {
+        super();
+    }
+
+    public NoAuthException(String message) {
+        super(message);
+    }
+
+    public NoAuthException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public NoAuthException(Throwable cause) {
+        super(cause);
+    }
+
+}
+
+```
+
+2.实现自定义异常处理器
+
+```java
+package com.heibaiying.exception;
+
+import org.springframework.web.servlet.HandlerExceptionResolver;
+import org.springframework.web.servlet.ModelAndView;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+/**
+ * @author : heibaiying
+ * @description : 无权限异常处理机制
+ */
+public class NoAuthExceptionResolver implements HandlerExceptionResolver {
+
+    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
+        if (ex instanceof NoAuthException && !isAjax(request)) {
+            return new ModelAndView("NoAuthPage");
+        }
+        return new ModelAndView();
+    }
+
+    // 判断是否是Ajax请求
+    private boolean isAjax(HttpServletRequest request) {
+        return "XMLHttpRequest".equalsIgnoreCase(request.getHeader("X-Requested-With"));
+    }
+}
+
+```
+
+3.在ServletConfig.java注册自定义异常处理器
+
+```java
+/**
+* 添加全局异常处理器
+*/
+public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) {
+    resolvers.add(new NoAuthExceptionResolver());
+}
+```
+
+4.定义测试controller，抛出自定义异常
+
+```java
+@Controller
+@RequestMapping("mvc")
+public class HelloController {
+
+    @RequestMapping("hello")
+    private String hello() {
+        return "hello";
+    }
+
+
+    @RequestMapping("auth")
+    private void auth() {
+        throw new NoAuthException("没有对应的访问权限！");
+    }
+}
+```
+
+注：调用这个controller时，同时也可以验证在拦截器部分提到的：如果对应的程序报错，拦截器不一定会进入postHandle这个方法 但一定会进入afterCompletion这个方法