Basic JSP syntax knowledge and basic jsp syntax knowledge

Basic JSP syntax knowledge and basic jsp syntax knowledge

1. JSP comments

Comments in JSP are classified into two categories:

Explicit comment: <! -- HTML comment, visible on the client --> (increase the transmission burden and minimize the use of data)
Implicit comment:
Format 1: // single line comment
Format 2:/**/single-line or multi-line comment
Format 3: <% -- JSP annotation, invisible to the client -- %> JSP Annotation
Example:
Compile a JSP file that contains the preceding three annotations

2. Scriptlet (script applet)

All Java programs embedded in HTML code must be marked with Scriptlet.
Scriptlet includes: Small scripts, declarations, and expressions.

(1) Small Script: <% Java code %>

Compile can write various statements in our Java application methods, including defining variables, but not methods.
Cause: the code will be converted into a method body in the class by the JSP Engine. If a method is written, it is equivalent
Declaration method, so the method cannot be written in a small script.

For example:

Calculate the sum of 1-100 on the Jsp page and output it on the page:

(2) Declaration: <%! Method %>

Compile defines global constants, writing method, but cannot be directly in <%! %> Write any common statement in it because this section is JSP
The engine is converted into a method in the class.
Note: JSP built-in objects cannot be used in this part.

For example:
Declare a method for formatting the date and call it to display the current date.

(3) expression: <% = %>

Outputs a variable or specific content.

For example:
Use out. print () and expression to print ten rows and ten columns of tables on the page. which method is better.
Out. print () output:

Expression output: it is more concise and the front-end code is more regular. Therefore, this method is recommended.