一点看法：
1.在jsp中，每一行标签都是一个参数，传给out.write()方法的参数，而表达式输出，仅仅是输出内容而已
2.输出脚本里面的内容是作为参数直接放入service方法的out输出流的打印流中的，所以也不用加分号结尾
3.代码脚本原封不动的加入到service方法的方法体，方便我们操作方法体中的对象以及做我们想做的一些判断等等
这是jsp页面的代码
<%@ page import="java.util.Date" %><%--
Created by IntelliJ IDEA.
User: Lenovo
Date: 2021/10/3
Time: 19:38
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
jsp测试
<%--
<%!…%>：声明，用来创建类的成员变量和成员方法(类似与类
--%>
<%--声明属性--%>
<%!
private int number;
private Date date;
private String name;
%>
<%--声明方法--%>
<%!
public void hello(){
System.out.println("我是jsp解析后的类的成员方法！");
}
%>
<%--声明内部类--%>
<%!
static class T{
static {
System.out.println("我是静态内部类的静态代码块！");
}
}
%>
然后我们找到tomcat翻译出来的.java文件
public final class test_jsp extends org.apache.jasper.runtime.HttpJspbase
implements org.apache.jasper.runtime.JspSourceDependent,
org.apache.jasper.runtime.JspSourceimports {
private int number;
private Date date;
private String name;
public void hello(){
System.out.println("我是jsp解析后的类的成员方法！");
}
static class T{
static {
System.out.println("我是静态内部类的静态代码块！");
}
}
private static final jakarta.servlet.jsp.JspFactory _jspxFactory =
jakarta.servlet.jsp.JspFactory.getDefaultFactory();
private static java.util.Map _jspx_dependants;
private static final java.util.Set _jspx_imports_packages;
private static final java.util.Set _jspx_imports_classes;
static {
_jspx_imports_packages = new java.util.HashSet<>();
_jspx_imports_packages.add("jakarta.servlet");
_jspx_imports_packages.add("jakarta.servlet.http");
_jspx_imports_packages.add("jakarta.servlet.jsp");
_jspx_imports_classes = new java.util.HashSet<>();
_jspx_imports_classes.add("java.util.Date");
}
private volatile jakarta.el.expressionFactory _el_expressionfactory;
private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager;
public java.util.Map getDependants() {
return _jspx_dependants;
}
public java.util.Set getPackageimports() {
return _jspx_imports_packages;
}
public java.util.Set getClassimports() {
return _jspx_imports_classes;
}
public jakarta.el.expressionFactory _jsp_getexpressionFactory() {
if (_el_expressionfactory == null) {
synchronized (this) {
if (_el_expressionfactory == null) {
_el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getexpressionFactory();
}
}
}
return _el_expressionfactory;
}
public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() {
if (_jsp_instancemanager == null) {
synchronized (this) {
if (_jsp_instancemanager == null) {
_jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
}
}
}
return _jsp_instancemanager;
}
public void _jspInit() {
}
public void _jspDestroy() {
}
public void _jspService(final jakarta.servlet.http.HttpServletRequest request, final jakarta.servlet.http.HttpServletResponse response)
throws java.io.IOException, jakarta.servlet.ServletException {
if (!jakarta.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {
final java.lang.String _jspx_method = request.getMethod();
if ("OPTIONS".equals(_jspx_method)) {
response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
return;
}
if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method)) {
response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSP 只允许 GET、POST 或 HEAD。Jasper 还允许 OPTIONS");
return;
}
}
final jakarta.servlet.jsp.PageContext pageContext;
jakarta.servlet.http.HttpSession session = null;
final jakarta.servlet.ServletContext application;
final jakarta.servlet.ServletConfig config;
jakarta.servlet.jsp.JspWriter out = null;
final java.lang.Object page = this;
jakarta.servlet.jsp.JspWriter _jspx_out = null;
jakarta.servlet.jsp.PageContext _jspx_page_context = null;
try {
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("rn");
out.write("rn");
out.write("rn");
out.write("rn");
out.write(" jsp测试 rn");
out.write("rn");
out.write("rn");
out.write('r');
out.write('n');
out.write('r');
out.write('n');
out.write('r');
out.write('n');
out.write('r');
out.write('n');
out.write('r');
out.write('n');
out.write('r');
out.write('n');
out.write("rn");
out.write("rn");
out.write("rn");
} catch (java.lang.Throwable t) {
if (!(t instanceof jakarta.servlet.jsp.SkipPageException)){
out = _jspx_out;
if (out != null && out.getBufferSize() != 0)
try {
if (response.isCommitted()) {
out.flush();
} else {
out.clearBuffer();
}
} catch (java.io.IOException e) {}
if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
else throw new ServletException(t);
}
} finally {
_jspxFactory.releasePageContext(_jspx_page_context);
}
}
}
发现我们在页面中写入的内容都在该类中加载了
再测试其他两个脚本，我这里直接混合使用了
<%
for(int i=1;i<=10;i++){
//使用输出流，将标签输出给浏览器
%>
你好
<%}%>
<%--
翻译出来的代码段
for(int i=1;i<=10;i++){
//使用输出流，将标签输出给浏览器
out.write("rn");
out.write("你好rn");
}
--%>
需要注意的是，标签不能直接写在java语句中，只能将Java语句拆分成几段脚本 ，让标签直接在body的下面才可以实现混合嵌套
