SpringBoot (三) --------- SpringBoot 和 web 组件

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一、SpringMVC 中使用拦截器

拦截器是 SpringMVC 中一种对象，能拦截对 Controller 对象的请求
拦截器框架中有系统的拦截器，还有自定义拦截器，实现对请求的预先处理

步骤 ：

• 自定义拦截器类，实现 HandlerInterceptor 接口

package com.fancy.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        return HandlerInterceptor.super.preHandle(request, response, handler);
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        HandlerInterceptor.super.afterCompletion(request, response, handler, ex);
    }
}

• 注册拦截器类

<mvc:interceptors>
    <mvc:interceptor>
        <mvc: path="url" />
        <bean class="拦截器的全限定名称">
    mvc:interceptor>
mvc:interceptors>

二、SpringBoot 中使用拦截器

步骤 ：

• 创建类实现 HandlerInterceptor 接口

package com.fancy.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("执行了 preHandle() 方法");
        return true;
    }
}

preHandle() 方法返回值 为 true 表示 请求能被 Controller 处理，返回值为false 表示请求被截断

• 注册拦截器对象

注册拦截器时需要加上 @Configuration 注解

package com.fancy.config;

import com.fancy.interceptor.MyInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class MyAppConfig implements WebMvcConfigurer {
     // 注册拦截器对象


    @Override
    public void addInterceptors(InterceptorRegistry registry) {

        // InterceptorRegistry 登记系统中可以使用的拦截器
        // 指定拦截的地址

        String path [] = {"/user/**"};
        String excludePath [] = {"/user/login"};

        registry.addInterceptor(new MyInterceptor()).addPathPatterns(path).excludePathPatterns(excludePath);
    }
}

addPathPatterns(path) 方法表示拦截路径为path的请求，excludePathPatterns(excludePath) 表示不拦截路径为 excludePath 的请求。 合起来就是 拦截 /user 下的所有请求除了 login

• 创建 controller 类

package com.fancy.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class BootController {
    @RequestMapping("/user/account")
    @ResponseBody
    public String queryAccount() {
        return "user/account";
    }
    
    @RequestMapping("/user/login")
    @ResponseBody
    public String login() {
        return "/user/login";
    }   
}

• 测试

prehandle 方法没有执行，表示请求没有被拦截

prehandle 方法执行，表示此请求被拦截

三、SpringBoot 中使用 Servlet

ServletRegistrationBean 用来做在 servlet 3.0+ 容器中注册 servlet 的功能，但更具有SpringBean 友好性。

• 创建 servlet

package com.fancy.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

public class MyServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
       
        resp.setContentType("text/html;charset=utf-8");
        PrintWriter out = resp.getWriter();
        out.println("使用 Servlet 对象");
        
        out.flush();
        out.close();
    }
}

• 注册 Servlet

第一种方式 ：

package com.fancy.config;

import com.fancy.servlet.MyServlet;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.servlet.Servlet;
import javax.servlet.ServletRegistration;

@Configuration
public class SystemConfig {
    
    @Bean 
    public ServletRegistrationBean servletRegistrationBean() {
   
    // 第一个参数是 servlet 对象, 第二个参数是 url pattern 
        ServletRegistrationBean reg = new ServletRegistrationBean(new MyServlet(), "/myservlet");
        return reg;
    }
}

第二种方式 ：

package com.fancy.config;

import com.fancy.servlet.MyServlet;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.servlet.Servlet;
import javax.servlet.ServletRegistration;

@Configuration
public class SystemConfig {

    @Bean
    public ServletRegistrationBean servletRegistrationBean() {
        ServletRegistrationBean reg = new ServletRegistrationBean(new MyServlet(), "/myservlet");

        ServletRegistrationBean bean = new ServletRegistrationBean();
        bean.setServlet(new MyServlet());
        bean.addUrlMappings("/login", "/test");
        return reg;
    }
}

• 测试结果

四、SpringBoot 中使用过滤器

Filter 是 Servlet 规范中的过滤器，可以处理请求，对请求的参数，属性进行调整，常常用来处理字符编码。

我们用 FilterRegistrationBean 来注册 Filter 对象。

• 创建 Filter 对象

package com.fancy.Filter;


import javax.servlet.*;
import java.io.IOException;

public class MyFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("使用了 Servlet 中的 Filter 对象");
        //请求继续向下执行
        filterChain.doFilter(servletRequest, servletResponse);
    }
}

• 注册 Filter

@Bean
public FilterRegistrationBean filterRegistrationBean() {
    FilterRegistrationBean reg = new FilterRegistrationBean();
    // 使用哪个过滤器
    reg.setFilter(new MyFilter());
    // 过滤器地址
    reg.addUrlPatterns("/user/*");
    return reg;
}

• **创建 Controller **

• 测试结果

五、SpringBoot 中配置字符集过滤器

• 注册 Filter

public FilterRegistrationBean filterRegistrationBean() {
	FilterRegistrationBean reg = new FilterRegistrationBean();
	// 创建CharacterEncodingFilter
	CharacterEncodingFilter filter = new CharacterEncodingFilter();
	// 设置 request, response 使用编码值
	filter.setEncoding("utf-8");
	// 强制request, response 使用 encoding 的值
	filter.setForceEncoding(true);
	reg.setFilter(filter);
	// 请求先使用过滤器处理
	reg.addUrlPatterns("/*");
	return reg;
}

• 在 application.properties 禁用SpringBoot 默认启用的过滤器

• 在 application.properties 文件中设置过滤器