我与404的不解之缘系列（一）记录一个智障一般的错误

自从学习了springboot和springcloud之后，一直都没有再用ssm。

今天，我决定复习一下ssm搭建，所以做了一个小项目，只有简简单单的查询数据功能，万万没想到，居然给我报了个404。

先上代码：以下代码中的注解，有一部分是我个人理解，可能有错误！

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:jee="http://www.springframework.org/schema/jee"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="    
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd  
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd  
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd  
        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-4.0.xsd  
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">
    
    <context:component-scan base-package="com.learn.ssm">
    <!-- context:component-scan对路径下的文件进行扫描，如果扫描到文件中带有@Service,@Component,@Repository,@Controller等这些注解的类，则把这些类注册为bean 
     -->
        
    </context:component-scan>
        
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="url" value="jdbc:mysql://127.0.0.1:3306/yxktv" />
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="username" value="root" />
        <property name="password" value="x5" />
    </bean>
    
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
    </bean>
    
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.learn.ssm.mapper" />
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property>
    </bean>
</beans>

springmvc.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:jee="http://www.springframework.org/schema/jee"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="    
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd  
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd  
        http://www.springframework.org/schema/mvc   http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd  
        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-4.0.xsd  
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">

    <mvc:annotation-driven />

    <!-- 静态资源配置 -->
    <mvc:resources mapping="/static/**" location="/static/" />

    <!-- 视图解析器 -->
    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/" />
        <property name="suffix" value=".jsp"></property>
    </bean>

    <!-- 使用注解的包，包括子集 -->
    <context:component-scan
        base-package="com.learn.ssm.controller" />


</beans>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>ssm</display-name>
  <context-param><!-- 初始化上下文参数 -->
    <param-name>contextConfigLocation</param-name>
    <param-value>classpath:applicationContext.xml</param-value>
  </context-param>
  <listener><!-- 监听器 用于监听种种操作，也可以自动激发一些操作 -->
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
  </listener>
  <servlet>
    <servlet-name>SpringMVC</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>classpath:springmvc.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
    <!-- load-on-startup 当值为0或者大于0时，表示容器在应用启动时就加载这个servlet；
当是一个负数时或者没有指定时，则指示容器在该servlet被选择时才加载。
正数的值越小，启动该servlet的优先级越高。
     -->
  </servlet>
  <servlet-mapping>
    <servlet-name>SpringMVC</servlet-name>
    <url-pattern>*.do</url-pattern>
    <!-- 如果url－pattern定义的是路径，那么以后所有对这个路径下资源的请求都会由servlet－name中定义的servlet处理.
            如果url－pattern定义的是资源格式例如*.do等，那么对于所有符合这种格式的资源的请求都由指定的servlet处理。
     -->
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>
</web-app>

SsmController.java

package com.learn.ssm.controller;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.learn.ssm.pojo.stu;
import com.learn.ssm.service.SsmService;

@RestController
@CrossOrigin

public class SsmController {
 @Autowired
 SsmService ssmService;
 @GetMapping("/show")
 public List<stu> show(){
  return ssmService.show();
 }
}

SsmMapper.xml

package com.learn.ssm.mapper;

import java.util.List;

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;

import com.learn.ssm.pojo.stu;

@Mapper
public interface SsmMapper {
 @Select("select * from stu")
 public List<stu> show();
}

SsmService.xml

package com.learn.ssm.service;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.learn.ssm.mapper.SsmMapper;
import com.learn.ssm.pojo.stu;

@Service
public class SsmService {
    @Autowired
    SsmMapper ssmMapper;
    public List<stu> show(){
        return ssmMapper.show();
    }
}

stu.java

package com.learn.ssm.pojo;

public class stu {
    
    String name;
    String sex;
    int id;
    int age;
    int date;
    int classs;
    int tall;
    int num;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public int getDate() {
        return date;
    }
    public void setDate(int date) {
        this.date = date;
    }
    public int getClasss() {
        return classs;
    }
    public void setClasss(int classs) {
        this.classs = classs;
    }
    public int getTall() {
        return tall;
    }
    public void setTall(int tall) {
        this.tall = tall;
    }
    public int getNum() {
        return num;
    }
    public void setNum(int num) {
        this.num = num;
    }
    
}

 当我在浏览器中输入http://localhost:8080/show.do时，报404，原因是我这个地址写错了，应该是http://localhost:8080/ssm20190627/show.do。

被自己蠢哭了... ...

再补充一点个人理解：

当启动tomcat之后，8080端口就会被tomcat占用，但是，在tomcat中是可以同时部署多个项目的，如果访问http://localhost:8080/show.do，那么访问的是哪一个项目呢？所以，需要加上项目名，用来加以区分，http://localhost:8080/ssm20190627/show.do。