Tomcat Notes: URL Mapping

This is a personal study notes of Apache Tomcat. Below are main reference material.

  • [1、URL Mapping To Resources](#1、URL Mapping To Resources)
    • [1.1、What we request for when hitting a URL](#1.1、What we request for when hitting a URL)
    • [1.2、Mapping Code](#1.2、Mapping Code)
      • [1.2.1、Mapping To Resources](#1.2.1、Mapping To Resources)
        • [1.2.1.1、Access Resourses in ROOT](#1.2.1.1、Access Resourses in ROOT)
      • [1.2.2、Mapping To Service](#1.2.2、Mapping To Service)

1、URL Mapping To Resources

1.1、What we request for when hitting a URL

When we hit a URL on browser like localhost:8080/example/hellowe are actually reqeusting a resource or service.

Resource refer to a file like .html,.image. For example when we hit example root full path which is localhost:8080/example, we are requesting index.htmland this file will be explained and rendered by browser and showed in a readable way.

I perceive those static files as a kind of resource.

But sometims we only request a service rather than a static file.

For example we click a buttton then browser sends a http request, supposing it's URL is https://www.system.com/delete?id=1.

A Tomcat application recieve the request and provide service which is deleting a record in database.

This is requesting for a servcie.

1.2、Mapping Code

Mapping to a resource is easy. It usually is like access file system.

But mapping to a service is more tricky.

I'm going to show how Tomcatmapping URL to a resource or service.

Supposing our web application's root URL is localhost:8080/myweb/

we have a war file like below. I omit some files for readability.

复制代码
myweb.war
----index.html
----assets
--------hello.img
----WEB-INF
---------web.xml
---------classes
-------------HelloServlet.class
----META-INF

1.2.1、Mapping To Resources

As i mentioned, mapping URL to a resource basically is similar to accessing a file in file system.

For example, If we want to get index.html, just call localhost:8080/myweb/index.html.

If wanting hello.img, just call localhost:8080/myweb/assets/hello.img.

So it's very similiar to file system.

Just notice that web root URL localhost:8080/myweb/represents hello.war's first level subdirectory. Then you can get all static resources hierarchyly just as the same way in file system.

1.2.1.1、Access Resourses in ROOT

Tomcat can have mutiple web applications which are located under webappsfolder.

复制代码
webapps
----myweb
----myweb1
----myweb2
----ROOT
---------root.txt

What I just showed is how to access static resources in myweb.

If accessig files in myweb, we should take localhost:8080/mywebas root URL.

If accessig files in myweb1, we should take localhost:8080/myweb1as root URL.

So mywebor myweb1is context which specifies which web apps you want to access.

Besides those web applicaton developed by programmer, Tomcatalways has a folder called ROOTunder webapps.

If you want to access static resources under ROOT, root.txtfor example, just remove the context and take localhost:8080/as the root URL representig the first level subdirectory of ROOT.

Thus just call localhost:8080/root.txtthen you can get root.txt.

1.2.2、Mapping To Service

Mapping URL to service could be more tricky. Because Java servlet classes usually have more deeper file structure, making URL too long.

复制代码
com.org.servlet.MyServlet.java			# It has 4 levels directory in total
acme.personnel.management.MedicalPlan	# very long

For readability Tomcat has a configuration file called web.xmlto map to resources with a more simple name.

Supposing we have a servlet called DeleteRecordServletwhose doGetmethod is to delete a record in database, whose location is myweb.war/com/org/servlet/DeleteRecordServlet.java.

复制代码
myweb.war			# omit some files
----com
--------org
------------servlet
----------------DeleteRecordServlet.java
----META-INF
--------web.xml
--------classes
------------com
----------------org
--------------------servlet
------------------------DeleteRecordServlet.class

Now we need to configure some mapping in web.xml, mapping a shorter url to DeleteRecordServlet.

xml 复制代码
<?xml version = "1.0" encoding = "ISO-8859-1"?>
<web-app>
    <servlet>
        <servlet-name>deleteServlet</servlet-name>
        <servlet-class>com.org.servlet.DeleteRecordServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>deleteServlet</servlet-name>
        <url-pattern>/delete</url-pattern>
    </servlet-mapping>
    
    <welcome-file-list>
      <welcome-file>index.html</welcome-file>
    </welcome-file-list>
</web-app>

In this way we can hit localhost:8080/myweb/deletewhich is more simple than normal url to call DeleteRecordServlet.

相关推荐
2301_77037373几秒前
Java集合
java·开发语言
哈喽姥爷8 分钟前
Spring Boot---自动配置原理和自定义Starter
java·spring boot·后端·自定义starter·自动配置原理
老华带你飞2 小时前
考研论坛平台|考研论坛小程序系统|基于java和微信小程序的考研论坛平台小程序设计与实现(源码+数据库+文档)
java·vue.js·spring boot·考研·小程序·毕设·考研论坛平台小程序
CHEN5_022 小时前
leetcode-hot100 11.盛水最多容器
java·算法·leetcode
songx_992 小时前
leetcode18(无重复字符的最长子串)
java·算法·leetcode
在路上`3 小时前
前端学习之后端java小白(三)-sql外键约束一对多
java·前端·学习
dazhong20123 小时前
Spring Boot 项目新增 Module 完整指南
java·spring boot·后端
xrkhy3 小时前
SpringBoot之日志处理(logback和AOP记录操作日志)
java·spring boot·logback
搬山境KL攻城狮3 小时前
MacBook logback日志输出到绝对路径
java·intellij-idea·logback
yb0os14 小时前
RPC实战和核心原理学习(一)----基础
java·开发语言·网络·数据结构·学习·计算机·rpc