[JAVA] What is JSP? ~ Let's know the basics of JSP !! ~

What is JSP

This time, I will explain ** "JSP" **, which is indispensable for creating web applications.

--What is JSP? --JSP components --Create and execute a JSP file

I will explain the above three points step by step.

What is JSP

"JSP (Java Server Pages)" is a server-side program technology similar to Servlet. Use ** JSP files ** instead of Servlet classes. JSP files are ** converted to Servlet classes when requested **, so what you can do with Servlet classes can also be done with JSP files. The advantage of using a JSP file is that ** it is possible to make HTML output very easy **. The JSP file is ** created by embedding Java code in HTML **. Embed Java code? I don't know if you say that, so let's see how to do it while looking at the following components of the JSP.

JSP components

The JSP file consists of ** HTML ** and ** Java code **. The part written in HTML is ** template ** The part written in Java code is called ** script **.

From here, it is a necessary element to create a basic JSP file ** ① "JSP comment" **, ** ② "page directive" **, ** ③ "scriptlet" **, ** ④ Learn more about "script expressions" **. Take a look at the sample code below.


<%--① JSP comment--%>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%><%--② page directive--%>
    String name="Yamazaki";
    int age=24;
    %><%--③ Scriptlet--%>
<!DOCTYPE html><%--template--%>
<meta charset="UTF-8">
my name is<%=name %>.. Age is<%=age %>I'm talented.<%--④ Script expression--%>

① "JSP comment"

<%-- ... --%>


<%--① JSP comment--%> 

However, when writing comments in scriptlets, it follows the Java syntax.


<%--① JSP comment--%> 
//Declare a variable

② "page directive"

<% @ page Attribute name = "value"%>

<%@ page language="java" contentType="text/html; charset=UTF-8"

You can use the page directive to make various settings related to the JSP file. Frequently used attributes are the contentType and import attributes.

③ "Scriptlet"

<% Java code%>


    String name="Yamazaki";
    int age=24;

Scriptlets allow you to embed Java code in JSP files.

④ "Script expression"

<% = Java code%>


my name is<%=name %>.. Age is<%=age %>I'm talented.

You can use script expressions to output variables, method return values, and so on.

Create and run a JSP file

To create a JSP file in Eclipse, select the dynamic web project for which you want to create an HTML file, right-click and select "New"-> "JSP File". jsp_create1.jpg

Specify the save location and file name of the file and press "Finish". By default, the "WebContent" directory is selected as the save location. jsp_create2.jpg

If you create a JSP file by the above method, Eclipse will write the minimum necessary contents such as ** page directive. ** **

<%@ page language="java" contentType="text/html; charset=UTF-8"
//<%Java code added here%>
<!DOCTYPE html>
<meta charset="UTF-8">
<title>Insert title here</title>
//<p>Write a paragraph here</p>

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