手写SpringMVC框架（一）-------项目搭建

SpringMVC处理请求的大致流程：



我们来开始着手手写一个SpringMVC框架。

新建一个springMVC项目，流程参见

SpringMVC框架搭建流程

引入servlet相关的jar包：

<dependency>
  <groupId>javax.servlet</groupId>
  <artifactId>javax.servlet-api</artifactId>
  <version>3.1.0</version>
</dependency>

新建一个servlet:

模拟springmvc，起名为LgDispatcherServlet

package com.lagou.edu.mvcframework.servlet;

import javax.servlet.http.HttpServlet;

/**
* @author liuyj
* @Title: LgDispatcherServlet
* @create 2020-06-11 14:22
* @ProjectName springmvc-demo
* @Description: TODO
*/
public class LgDispatcherServlet extends HttpServlet {
}

web.xml中注册我们新建的LgDispatcherServlet：

<servlet>
  <servlet-name>lgmvc</servlet-name>
  <servlet-class>com.lagou.edu.mvcframework.servlet.LgDispatcherServlet</servlet-class>
</servlet>

<servlet-mapping>
  <servlet-name>lgmvc</servlet-name>
  <url-pattern>/*</url-pattern>
</servlet-mapping>

新建几个自定义注解：

@Documented
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface LagouAutowired {
     String value() default "";
}

@Documented
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface LagouController {
     String value() default "";
}

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

@Documented
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface LagouService {
     String value() default "";
}

新建demo包下的service及implement实现类及controller并加上相应的注解：

service:

package com.lagou.edu.demo.service;

public interface IDemoService {

    String get(String name);
}

impl:

package com.lagou.edu.demo.service.impl;

import com.lagou.edu.demo.service.IDemoService;
import com.lagou.edu.mvcframework.annotations.LagouService;

@LagouService("demoService")
public class DemoServiceImpl implements IDemoService {
    @Override
    public String get(String name) {
        System.out.println("service 实现类中的name参数：" + name) ;
        return name;
    }
}

controller:

package com.lagou.edu.demo.controller;

import com.lagou.edu.demo.service.IDemoService;
import com.lagou.edu.mvcframework.annotations.LagouAutowired;
import com.lagou.edu.mvcframework.annotations.LagouController;
import com.lagou.edu.mvcframework.annotations.LagouRequestMapping;

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

@LagouController
@LagouRequestMapping("/demo")
public class DemoController {

    @LagouAutowired
    private IDemoService demoService;

    /**
     * URL: /demo/query?name=lisi
     * @param request
     * @param response
     * @param name
     * @return
     */
    @LagouRequestMapping("/query")
    public String query(HttpServletRequest request, HttpServletResponse response,String name) {
        return demoService.get(name);
    }
}

本节到此结束。

下一节我们来开始结构开发设计。

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