1 Overview

1. What is JSP?

Java Server Pages, the server-side technology responsible for page display, can nest Java language to replace the way of using Servlet to generate pages,The bottom layer is converted into Servlet .

Second path

1. Absolute path

The resource can be uniquely determined by itself The path starts with the protocol, such as http in an HTTP request.

2. Relative path

You must rely on other paths to uniquely determine the path of the resource, and the content does not start with a protocol.

3. Resource path composition

Access path + resource name, the resource name is the content after the last "/", and the rest is access path.

4. WEB-INF path

Resources placed in the WEB-INF directorycan only be forwarded through programs Visit, which cannot be accessed directly through the browser and is relatively safe. When the redirect is executed, the address is sent to thebrowser, and the browser makes the request. Therefore, the redirect within the program cannot directly access the resources in the WEB-INF directory.
In the resources under the WEB-INF directory, only the path relative to the server can be used, and the path relative to the current resource access path cannot be used, that is, the following path form can only be used:

${pageContext.request.contextPath}/xxx

5. Redirect path

All redirections can only be in the form of paths relative to the server, because redirection can To access resources in other projects, the starting point of the path is the server. According to the change of the address in the address bar, all requests in HTML pages and JSP pages can be regarded as redirects, and all paths must be in a form relative to the server.

6. Forwarding path

All forwarding can only be in the form of a path relative to the project, because forwarding can only access files within the same project resource.

Three command tags

is used to set information that is valid in the entire JSP page. The syntax format of the command tag is:

<%@ tagName attr="value"...%>

There are three instruction identifiers in JSP:

1.page

The main attributes used are:

• contentType: Set the MIME type and encoding method of the page.

• isErrorPage: Set the page as an error handling page. It is usually used in combination with the built-in object exception to handle the error information of another page.

• errorPage: Specify the error handling page for the page. When an error occurs when the page is running, jump to the specified page.

2.include

<%@ include file="path"%>

Static inclusion, used to include a JSP page in the current page. The so-called static inclusion means that the included JSP page is presented as it is in the containing page, and the same Servlet is generated as thecontaining page.

3.taglib

<%@ taglib prefix="c"uri=""%>

is used to introduce the tag library to the current page and use the specified prefix to reference the tag library tags in .

Four action identifiers

There are 3 action identifiers in JSP:

1.< ;jsp:include>

Dynamic inclusion is used to include a JSP page in the current page. The so-called dynamic inclusion means that the included page is compiled and presented in the current page.The including page and the included page each generate a Servlet.

2.

is used for page jump.

3.

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