How to output HTML from JSP <%! … %> block?

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温柔的废话

I just started learning JSP technology, and came across a wall.

How do you output HTML from a method in <%! ... %> JSP declaration block?

This do

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刺人心

2020-12-01 10:44

<%!
private void myFunc(String Bits, javax.servlet.jsp.JspWriter myOut)
{  
  try{ myOut.println("<div>"+Bits+"</div>"); } 
  catch(Exception eek) { }
}
%>
...
<%
  myFunc("more difficult than it should be",out);
%>

Try this, it worked for me!

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情书的邮戳

2020-12-01 10:49
I suppose this would help:
```
<%! 
   String someOutput() {
     return "Some Output";
  }
%>
...
<%= someOutput() %>
```
Anyway, it isn't a good idea to have code in a view.
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一生所求

2020-12-01 10:50
You can do something like this:
```
<%

out.print("<p>Hey!</p>");    
out.print("<p>How are you?</p>");

%>
```
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無奈伤痛

2020-12-01 10:51
You can do something like this:
```
<%!
String myMethod(String input) {
    return "test " + input;
}
%>

<%= myMethod("1 2 3") %>
```
This will output test 1 2 3 to the page.
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佛祖请我去吃肉

2020-12-01 10:55

You can't use the 'out' variable (nor any of the other "predeclared" scriptlet variables) inside directives.

The JSP page gets translated by your webserver into a Java servlet. Inside tomcats, for instance, everything inside scriptlets (which start "<%"), along with all the static HTML, gets translated into one giant Java method which writes your page, line by line, to a JspWriter instance called "out". This is why you can use the "out" parameter directly in scriptlets. Directives, on the other hand (which start with "<%!") get translated as separate Java methods.

As an example, a very simple page (let's call it foo.jsp):

<html>
    <head/>
    <body>
        <%!
            String someOutput() {
                return "Some output";
            }
        %>
        <% someOutput(); %>
    </body>
</html>

would end up looking something like this (with a lot of the detail ignored for clarity):

public final class foo_jsp
{
    // This is where the request comes in
    public void _jspService(HttpServletRequest request, HttpServletResponse response) 
        throws IOException, ServletException
    {
        // JspWriter instance is gotten from a factory
        // This is why you can use 'out' directly in scriptlets
        JspWriter out = ...; 

        // Snip

        out.write("<html>");
        out.write("<head/>");
        out.write("<body>");
        out.write(someOutput()); // i.e. write the results of the method call
        out.write("</body>");
        out.write("</html>");
    }

    // Directive gets translated as separate method - note
    // there is no 'out' variable declared in scope
    private String someOutput()
    {
        return "Some output";
    }
}

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被撕碎了的回忆

2020-12-01 10:56

too late to answer it but this help others

<%! 
     public void printChild(Categories cat, HttpServletResponse res ){
       try{
          if(cat.getCategoriesSet().size() >0){
              res.getWriter().write("") ; 
          }
       }catch(Exception exp){

       }
     }

%>

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