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JSP: Actions basics

Actions are marginally nicer versions of scriptlets, at least some actions that you can perform in scriptlets.

    <jsp:include page="some.jsp">
       <jsp:param name="hi" value="there />
    </jsp:include>

This will include a file like scriptlet, but it’s run at runtime, so the page value can be dynamically created.

You can import a Java bean (a getter and setter object with an empty constructor).

    <%@ page import="thing.Hello" %>
    <jsp:useBean id="bean" class="thing.Hello" />

The actual bean is this is simple enough:

    package thing;
    public class Bean {

       private String thing = "";

       public String getThing() {
         return thing;
       }

       public void setThing(String thing) {
         this.thing = thing;
       }
    }

Now you can access it using a scriptlet using the variable ‘bean’. You can also use the getProperty and setProperty action:

    <jsp:setProperty name="bean" property="thing" value="SAAATTAAAN" />

    <jsp:getProperty name="bean" property="thing" />

You can also use the getProperty and setProperty actions to manipulate request parameters. Below we set the object based on the URL parameter other:

    <jsp:setProperty name="bean" property="thing" param="other" />

If you omit the ‘param’ part, we’ll set the thing property via thing in the URL, example.com/hiya?thing=THIS, for example. Or if we put a ‘*’ in the property we’ll set the entire bean via parameter properties.

You can also forward pages to another page, and pass parameters there:

    <% if(bean.getThing().equals("SAAAATAAAAAN")) { %>
       <jsp:forward page="e.jsp">
         <jsp:param name="hi" value="X" />
       </jsp:forward>
    <% } %> 
java jsp jsp-actions

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