问题：
- jsp 中如果 include 了其他的 jsp 页面时 request 属性是否能传递到 include 的页面中
测试
新建一个 IndexServlet 为 request 设置 name 属性并 forward 到 index.jsp. index.jsp 包含一个子页面 mypage.jsp 这个页面会拿尝试那 index.jsp 中的 request 属性并显示
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| public class IndexServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setAttribute("name", "jack");
RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/index.jsp");
dispatcher.forward(req, resp);
}
}
|
jsp 页面代码如下
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| <!-- index.jsp -->
<html>
<body>
<h2>Hello World!</h2>
<jsp:include page="mypage.jsp"/>
</body>
</html>
<!-- mypage.jsp -->
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<h2>Name: <%=request.getAttribute("name")%></h2>
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配置 web.xml 指定路由
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| <servlet>
<servlet-name>IndexServlet</servlet-name>
<servlet-class>com.jzheng.servlet.IndexServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>IndexServlet</servlet-name>
<url-pattern>/indexServlet</url-pattern>
</servlet-mapping>
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启动 server 时跳出来的首页，name 为 null, 访问 /indexServlet 显示的首页 name 属性可以被拿到
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| curl 'http://localhost:8080/'
<html>
<body>
<h2>Hello World!</h2>
<h2>Name: null</h2>
</body>
</html>
curl 'http://localhost:8080/indexServlet'
<html>
<body>
<h2>Hello World!</h2>
<h2>Name: jack</h2>
</body>
</html>
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探究
Mac 环境下配置的 Tomcat 服务，jsp 编译的页面会放在 /Users/jack/Library/Caches/JetBrains/IntelliJIdea2021.1/tomcat/a0a1bd57-0f17-404d-9ff8-9f185e6d4d97/work/Catalina/localhost/ROOT/org/apache/jsp 这个路径下
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| .
├── index_jsp.class
├── index_jsp.java
├── mypage_jsp.class
└── mypage_jsp.java
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index_jsp.java 和 mypage_jsp.java 核心代码显示如下
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|
response.setContentType("text/html");
pageContext = _jspxFactory.getPageContext(this, request, response, null, true, 8192, true);
_jspx_page_context = pageContext;
application = pageContext.getServletContext();
config = pageContext.getServletConfig();
session = pageContext.getSession();
out = pageContext.getOut();
_jspx_out = out;
out.write("<html>\n");
out.write("<body>\n");
out.write("<h2>Hello World!</h2>\n");
out.write("\n");
org.apache.jasper.runtime.JspRuntimeLibrary.include(request, response, "mypage.jsp", out, false);
out.write("\n");
out.write("</body>\n");
out.write("</html>\n");
response.setContentType("text/html;charset=UTF-8");
pageContext = _jspxFactory.getPageContext(this, request, response, null, true, 8192, true);
_jspx_page_context = pageContext;
application = pageContext.getServletContext();
config = pageContext.getServletConfig();
session = pageContext.getSession();
out = pageContext.getOut();
_jspx_out = out;
out.write("\n");
out.write("<h2>Name: ");
out.print(request.getAttribute("name"));
out.write("</h2>\n");
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可以看到父页面中通过 org.apache.jasper.runtime.JspRuntimeLibrary.include(request, response, "mypage.jsp", out, false); 包含页面，这个过程中是会把 request 当成参数传递的，自然在自页面中是能访问到这个对象的。
PS: 在配置 Tomcat 服务器时有两种 type, Tomcat 和 TomEE 之前选错了 TomEE 起不来 server （；￣ェ￣）