Understanding include in JSP (i): include-file instruction Test

Include|js First Example:

INCLUDE-FILE-TEST-1.JSP:

<%@ page contenttype= "TEXT/HTML;CHARSET=GBK"%>
<%! String dec_str = "Dec_str";%>
<%=dec_str%><br>
<%@ include file= "include-file-test-2.jsp"%><br>
<%=dec_str%><br>

INCLUDE-FILE-TEST-2.JSP:

<%@ page contenttype= "TEXT/HTML;CHARSET=GBK"%>
<%
Dec_str = "Scr_str"; Eclipse displays an error.
%>

Results:

Dec_str

Scr_str

Conclusion: the instance variable (or local variable) defined in File1, file2 can be referenced and changed. But direct access to File2 can be an error.



A second example:

INCLUDE-FILE-TEST-1.JSP:

<%@ page contenttype= "TEXT/HTML;CHARSET=GBK"%>

<% scr_str = "Hello" + scr_str;%>

<%@ include file= "include-file-test-2.jsp"%>
<%=scr_str%><br>
<% temp = "Hello" + temp;%>
<%=temp%>

INCLUDE-FILE-TEST-2.JSP:

<%@ page contenttype= "TEXT/HTML;CHARSET=GBK"%>
<%! String scr_str = "Scr_str";%>
<% String temp = "temp"; %>

View the file1 corresponding servlet:

Package org.apache.jsp.jsp_002dsyntax_002dtest;

Import ... ；

Public final class include_002dfile_002dtest_002d1_jsp ... {

String scr_str = "Scr_str";
private static Java.util.Vector _jspx_dependants;

static {
_jspx_dependants = new Java.util.Vector (1);
_jspx_dependants.add ("/jsp-syntax-test/include-file-test-2.jsp");
}

Public Java.util.List getdependants () {
return _jspx_dependants;
}

public void _jspservice (HttpServletRequest request, httpservletresponse response)
Throws Java.io.IOException, Servletexception {

......
try {
......

Response.setcontenttype ("TEXT/HTML;CHARSET=GBK");
......

Scr_str = "Hello" + scr_str;
The String temp = "temp";
......
Out.print (SCR_STR);
temp = "Hello" + temp;
......

Out.print (temp);
catch (Throwable t) {
......

finally {
......
}
}
}

Results:

Hello Scr_str
Hello Temp

Conclusion: the instance variable defined in File2, file1 can be referenced and changed before (or after) the <%@ include file= ""%> directive.

Local variables defined in File2, file1 must be referenced and changed after the <%@ include file= ""%> directive.



A third example:

INCLUDE-FILE-TEST-1.JSP:

<%@ page contenttype= "TEXT/HTML;CHARSET=GBK"%>
<%!
String str1 = "str1";
%>
<%
String STR4 = str1 + str2 + str3;
%>
<%@ include file= "include-file-test-2.jsp"%>
<%=str4%>

INCLUDE-FILE-TEST-2.JSP:

<%@ page contenttype= "TEXT/HTML;CHARSET=GBK"%>
<%!
String str2 = "str2";
String STR3 = str1 + str2;
%>

File1 corresponds to the servlet:

Package org.apache.jsp.jsp_002dsyntax_002dtest;

Import ...

Public final class include_002dfile_002dtest_002d1_jsp ... {


String str1 = "str1";


String str2 = "str2";
String STR3 = str1 + str2;

......

public void _jspservice (HttpServletRequest request, httpservletresponse response)
Throws Java.io.IOException, Servletexception {

......


try {
......
Response.setcontenttype ("TEXT/HTML;CHARSET=GBK");
......

String STR4 = str1 + str2 + str3;

......
Out.print (STR4);
catch (Throwable t) {
......
}




Results:

STR1 str2 str1 str2



Conclusion: File2 does not generate a servlet, but its contents are included in the File1-generated servlet, and file2 itself is added to a vector-type class variable named "_jspx_dependants". As you can see, the instance variable "SCR_STR" defined in File2 is moved to the File1-generated servlet. It can be seen that Tomcat is dealt with in a very intriguing mechanism.