# 1/9 Servlet 觀念

###### tags: `Servlet`

# 4-57 Servlet文件上傳
可與HTML form標籤一起用
# 4-58 html文件上傳表單
# 4-59 UploadFileDemo
File Uploading Form(單筆上傳)
Multiple Files Upload(多筆上傳)
上傳路徑(multipart/form-data)

<form action = "UploadServlet" method = "post" enctype = "multipart/form-data">

# java servlet Annotation
Annotation -> @
@MultipartConfig
https://docs.oracle.com/javaee/6/tutorial/doc/gmhal.html
UploadServlet.java 裡面註解
smartupload
https://codertw.com/%E7%A8%8B%E5%BC%8F%E8%AA%9E%E8%A8%80/302309/
# 4-62 ServletResponse介面
https://javaee.github.io/javaee-spec/javadocs/
# 4-62 HttpServletResponse介面
setHeader
https://javaee.github.io/javaee-spec/javadocs/
# 4-66 Status Code分類
100-199 文字錯誤
200-299 ok
300-399 東西不存在
400-499 錯誤
500-599 伺服器有問題
# 4-67.71 sendError sendRedirect
SearchNewsServlet.java
sendRedirect()告訴客戶端到另一個瀏覽器
# 4-75 servlet & deployment descriptor
WEB-INF->web.xml
Servlet ->web.xml(舊版)
Servlet ->Annotation(@)(新版)
# 4-77.78 Servlet Filter(過濾器)
Client(客戶端)<->server 兩邊都能用
用法 78頁
# 4-83 LogFilter.java
https://javaee.github.io/javaee-spec/javadocs/
chain - the FilterChain for invoking the next filter or the resource
/* 萬用資源每個都能偵查
# 4-85.86 life Cycle of Servlet & Servlet的起始設定
init
https://javaee.github.io/javaee-spec/javadocs/
override 覆寫
# 轉型
sendError

import javax.servlet.http.*;
((HttpServletResponse)response).sendError(HttpServletResponse.SC_FORBIDDEN,"123");

# 4-88 Servlet載入與產生
被動式啟動
Preloading不會先啟動,值越小的越優先,-1永遠不啟動
https://www.javatpoint.com/load-on-startup
# 4-91 ServletConfig介面
https://javaee.github.io/javaee-spec/javadocs/
ServletConfig 讀取參數為主
Servletcontainer 不同環境
# 4-92 webdome
web.xml 不同名註冊

<servlet>
    <description></description>
    <display-name>EnglishGreeting</display-name>
    <servlet-name>EnglishGreeting</servlet-name>
    <servlet-class>GreetingServlet</servlet-class>
    <init-param>
      <param-name>greetingText</param-name>
      <param-value>Hello</param-value>
    </init-param>
  </servlet>
  <servlet-mapping>...

# 4-95 GreetingServlet.JAVA web.xml
# 4-97.98.104 war
war=>web app
# Export war
放apache下面
# 4-107 init-param

<param-name>參數名稱是唯一的
<param-value>定義參數的值

# 4-109 Mapping a URL to a servlet
/Context/servlet path