SpringMVC使用

SpringMVC:Java实现的MVC轻量级框架

MVC:模型视图控制器

最典型的mvc架构就是:jsp + service + servlet .

Model2时代演变成mvc架构,

以前是jsp(jsp本身就是servlet)+dao = 视图层 + 模型层

架构一定是演进过来的(ALL in One)

<<淘宝的十年架构>> 淘宝技术这十年架构发展_Apple_Web的博客-CSDN博客

王坚:去IOE化

方便团队开发,java是项目越大,越好开发

特点

约定优于配置

中心控制器DispatchServlet

回顾Servlet

尽量用**add framework support(添加框架支持)**来添加web目录,保证web.xml是最新的

M V VM:ViewModel(双向绑定)

HelloSpringMVC 运行原理

客户端发送请求
DispatcherServlet(核心控制分发器)根据请求,找到处理器映射器和处理器适配器,让他们去执行一个servlet

SpringMVC会调用DispatchServlet的doService(),debug可以看到

protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {

这个servlet实现了Controller,就是一个Controller(控制器)了.
实现其中的方法,必须返回一个ModelAndView,相当于告诉DispatcherServlet,去哪个视图,和怎么处理数据.
DispatcherServlet找到对应的视图,渲染数据后响应回客户端

spring-webmvc包含了所有spring和springmvc会用到的jar包


  org.springframework
  spring-webmvc
  5.3.14

web.xml配置DispatcherServlet及映射

java项目中的classpath到底是什么

＜load-on-startup＞1＜/load-on-startup＞的作用


  springmvc
  
  org.springframework.web.servlet.DispatcherServlet
  
    
    contextConfigLocation
    
      

      
      true

ModelMap家族

注解开发

web.xml不变,spring-servlet.xml配置注解相关

default和annotation是不处理静态资源,如css文件,和自动注入(省略注解适配器和解析器)

真实的controller类

使用注解Controller后,就必须配置注解解析器

package com.changGe.li.servlets;

import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;

//被Spring接管,
//其下所有方法只要返回值是String,就会被视图解析器解析
@org.springframework.stereotype.Controller

//http://localhost:8080/SpringMVC/hello/SpringMVC
@RequestMapping("/hello")
public class HelloSpringMVC {

  @RequestMapping("/SpringMVC")
  public String helloSpringMVC(Model model){
    model.addAttribute("msg","helloSpringMVC");

    return "hello";
  }

}

两个不同的路径,最后都跳转到同一个页面,这个是博客网站的思想,页面复用

@org.springframework.stereotype.Controller
@RequestMapping("/hello")
public class HelloSpringMVC {

  @RequestMapping("/SpringMVC")
  public String helloSpringMVC(Model model){
    model.addAttribute("msg","helloSpringMVC");

    return "hello";
  }


  @RequestMapping("/Spring")
  public String helloSpring(Model model){
    model.addAttribute("msg","helloSpringMVC");

    //文件名中尽量不要用数字,就用英文就好
    return "test";
  }

}

RestFul风格:通过相同的请求方式实现不同的效果

RequestMapping源码中的value别名是path

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package org.springframework.web.bind.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.core.annotation.AliasFor;

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Mapping
public @interface RequestMapping {
  String name() default "";

  @AliasFor("path")//定义别名
  String[] value() default {};

  @AliasFor("value")
  String[] path() default {};

  RequestMethod[] method() default {};

  String[] params() default {};

  String[] headers() default {};

  String[] consumes() default {};

  String[] produces() default {};
}

@org.springframework.stereotype.Controller
public class HelloSpringMVC {

  @RequestMapping(path ="/mvc/{a}/{b}",method = RequestMethod.GET)
  public String helloSpringMVC(@PathVariable("a") int a,@PathVariable("b") int b, Model model){
    model.addAttribute("msg",a+b);

    return "hello";
  }

  
	//这里有bug,报404,暂时没有找到原因
  @PostMapping("/post/{a}/{b}")
  public String helloSpring(@RequestParam("a") int a, @RequestParam("b") int b, Model model){
    model.addAttribute("msg",a+b);

    return "hello";
  }

}

转发和重定向

有视图解析器的情况下,默认是转发

把springmvc-servlet.xml中的视图解析器注掉

@RequestMapping(path ="/mvc/{a}/{b}")
public String helloSpringMVC(@PathVariable("a") int a,@PathVariable("b") int b, Model model){
  model.addAttribute("msg",a+b);

  //没有视图解析器:转发
  return "forward:/WEB-INF/jsp/hello.jsp";
}

@RequestMapping("/get")
public String helloSpring(){
  //重定向
  return "redirect:/index.jsp";
}

过滤器

springMVC的乱码过滤

web.xml


  encodingFilter
  org.springframework.web.filter.CharacterEncodingFilter
  
    
    encoding
    utf-8
  


  encodingFilter
  /
  
public class GenericEncodingFilter implements Filter {
 
   @Override
   public void destroy() {
  }
 
   @Override
   public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
       //处理response的字符编码
       HttpServletResponse myResponse=(HttpServletResponse) response;
       myResponse.setContentType("text/html;charset=UTF-8");
 
       // 转型为与协议相关对象
       HttpServletRequest httpServletRequest = (HttpServletRequest) request;
       // 对request包装增强
       HttpServletRequest myrequest = new MyRequest(httpServletRequest);
       chain.doFilter(myrequest, response);
  }
 
   @Override
   public void init(FilterConfig filterConfig) throws ServletException {
  }
 
}
 
//自定义request对象，HttpServletRequest的包装类
class MyRequest extends HttpServletRequestWrapper {
 
   private HttpServletRequest request;
   //是否编码的标记
   private boolean hasEncode;
   //定义一个可以传入HttpServletRequest对象的构造函数，以便对其进行装饰
   public MyRequest(HttpServletRequest request) {
       super(request);// super必须写
       this.request = request;
  }
 
   // 对需要增强方法 进行覆盖
   @Override
   public Map getParameterMap() {
       // 先获得请求方式
       String method = request.getMethod();
       if (method.equalsIgnoreCase("post")) {
           // post请求
           try {
               // 处理post乱码
               request.setCharacterEncoding("utf-8");
               return request.getParameterMap();
          } catch (UnsupportedEncodingException e) {
               e.printStackTrace();
          }
      } else if (method.equalsIgnoreCase("get")) {
           // get请求
           Map parameterMap = request.getParameterMap();
           if (!hasEncode) { // 确保get手动编码逻辑只运行一次
               for (String parameterName : parameterMap.keySet()) {
                   String[] values = parameterMap.get(parameterName);
                   if (values != null) {
                       for (int i = 0; i < values.length; i++) {
                           try {
                               // 处理get乱码
                               values[i] = new String(values[i]
                                      .getBytes("ISO-8859-1"), "utf-8");
                          } catch (UnsupportedEncodingException e) {
                               e.printStackTrace();
                          }
                      }
                  }
              }
               hasEncode = true;
          }
           return parameterMap;
      }
       return super.getParameterMap();
  }
 
   //取一个值
   @Override
   public String getParameter(String name) {
       Map parameterMap = getParameterMap();
       String[] values = parameterMap.get(name);
       if (values == null) {
           return null;
      }
       return values[0]; // 取回参数的第一个值
  }
 
   //取所有值
   @Override
   public String[] getParameterValues(String name) {
       Map parameterMap = getParameterMap();
       String[] values = parameterMap.get(name);
       return values;
  }
}

JSON

切记,更新一次maven,就去配置一次项目设置中的工件

SpringMVC默认就是jackson


  com.fasterxml.jackson.core
  jackson-databind
  2.13.1

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
  
    private String name;
    private int age;
    private char sex;
    
}

@RestController = @Controller + @ResponseBody组成

ResponseBody可以规定不走视图解析器,返回值是字符串

@RestController
public class HelloSpringMVC {

  //解决中文乱码
  @RequestMapping(value = "/mvc",produces ="application/json;charset=utf-8")
  @ResponseBody
  public String helloSpringMVC() throws Exception{

    ObjectMapper mapper = new ObjectMapper();
    User user = new User("李长歌", 18, '女');

    return mapper.writeValueAsString(user);
  }

}

Json返回时间戳的工具类

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

import java.text.SimpleDateFormat;

public class JsonUtils {

    //传入一个时间,将其转换格式
    public static String getJson(Object object){
        return getJson(object,"yyyy-MM-dd HH:mm:ss");
    }

    public static String getJson(Object object,String dateFormat){
        ObjectMapper mapper = new ObjectMapper();

        //不使用时间戳
        mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS,false);

        SimpleDateFormat simpleDateFormat = new SimpleDateFormat(dateFormat);

        mapper.setDateFormat(simpleDateFormat);

        String s = null;
        try {
            s = mapper.writeValueAsString(object);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }

        return s;

    }

}

@RequestMapping(value = "/mvc",produces ="application/json;charset=utf-8")
public String helloSpringMVC(){

  Date date = new Date();

  return JsonUtils.getJson(date);
}

FastJson


  com.alibaba
  fastjson
  1.2.73

@org.junit.Test
  public void test(){
  User user = new User();
  User user1 = new User();

  ArrayList

SpringMVC使用

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