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Editor to share with you how to achieve JSP HTML form, I believe that most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to understand it!

In most cases, commercial websites need to have some forms, such as entering a consumer's name and address, or typing a word to check it with a search engine, or marketers collect some data from visitors for reference.

What do you do with the data returned by those forms?

The visitor enters data into the JSP engine through the form and saves it in the request object, so what happens next?

The JSP engine then passes the response object to the JSP page, which contains the defined format and data from the server. At this point, the JSP engine and the Web server send a sorted and complete page to the customer, which is what they see on the browser. The communication protocol between the client and the server can use HTTP, of course, can also use other.

Request and Response objects play a role in the original JSP code you create. When it comes to how to use the request object, I will explain it to you in more detail.

How to create a form, then this JSP tutorial will show you a step:

Use HTML to define some representative forms to make a JSP file, and then use JSP tags to pass data on forms and server-side objects (usually in Bean). Here's what you usually do:

1. Write the original JSP file, create some HTML forms and name them.

2. Write Bean in the Java file, define properties, GET or SET methods to match the form that you have assigned a name.

3. Go back to the original JSP file and add tags to create or call a ready-made Bean.

4. Add the tag to set the attribute of the Bean that needs the SET method in the HTML form.

5. Add the tag to set the attribute of the Bean that needs the GET method in the HTML form.

6. If you need to process more user data, use the request object.

You may not understand it after talking for a long time, but in fact, you can understand it by looking at an example.

Let's start with a simple example of hello:

In fact, this program is still the most classic "hello,world" program in the computer program, but I made him twist a little to make him look more intelligent and complicated. First you enter your name, and then Duke says to you, "hello!"

JSP source code:

Dukebanner.html < table border= "0" width= "400" cellspacing= "0" cellpadding= "0 > < tr > < td height=" 150 "width=" 150 "> < / td > < td width= < / td > < / tr > < tr > < td width=" 150 "> < / td > < td align=" right "width=" 250 "> < img src=" duke.waving.gif "> < / td > < / tr > < / table > < br > main JSP file: hellouser.jsp <% @ page import= "hello.NameHandler"% > < jsp:useBean id= "mybean" scope= "page" class= "hello.NameHandler" / > < jsp:setProperty name= "mybean" property= "*" / > < html > < head > < title > Hello User < / title > < / head > < body bgcolor= "# ffffff" background= "background.gif" > <% @ include file= "dukebanner.html"% > < table border= "0" width= "700" > < tr > < td width=" 150" > < / td > < td width= "550" > < H2 > My name is Duke. What's yours? < / H2 > < / td > < / tr > < tr > < td width= < / td > < td width= "550" > < form method=" get "> < input type=" text "name=" username "size=" 25 "> < br > < input type=" submit "value=" Submit "> < input type=" reset "value=" Reset "> < / td > < / tr > < / form > < / table > <% If (request.getParameter ("username")! = null) {% > <% @ include file= "response.jsp"% > <%}% > < / body > < / html > response file: response.jsp < table border= "0" width= "700" > < tr > < td width=" 150 "> < / td > < td width=" 550" > < H2 > Hello < jsp:getProperty name= "mybean" property= "username" / >! < / H2 > < / td > < / tr > < / table > Bean: (namehandler.java) package hello for processing data Public class NameHandler {private String username; public NameHandler () {username = null;} public void setUsername (String name) {username = name;} public String getUsername () {return username;}}

Create a HTML form

The window of a HTML is divided into three parts:

Label, input method, submit button to send data to the server. General HTML page, is written like this, in other pages of the action attribute may be other special CGI programs or other procedures that can deal with data, then how to use it in JSP, ah, if you want to send the data to Bean, then you can omit the action inside the East, directly write tags or other specific JSP file. The next forms are pretty much the same as normal HTML, the < INPUT > method, and then add a submit button, maybe a Reset button, and, by the way, don't forget, add a name to each input form.

Write as follows: < INPUT name=username >

Using the GET and POST methods

GET and POST methods can be used to send data to the server. In JSP programs, GET and POST methods can send data to Bean, servlet, or other server-side components.

In theory, GET requests data from the server, and POST sends data to the server. In fact, the GET method adds the data parameter queue (query string) to a URL, and the value corresponds to the form one by one. For example, name=John. In the queue, values and forms are separated by a & sign, spaces are replaced by a + sign, and special symbols are converted into hexadecimal codes. Because the queue is in URL, the parameters of the queue can be seen, recorded, or changed. Usually the GET method also limits the size of characters. In fact, the POST method can transmit data to the server without time limit, and the user cannot see this process on the browser side, so the POST method is more suitable for sending a secret (such as a credit card number) or a relatively large amount of data to the server.

Write Bean

If the JSP program uses Bean, you have to design your Bean according to JavaBeans API's instructions.

Remember the following two key parts.

If you use tags in JSP programs, you have to match the GET method in Bean.

If the JSP program goes on to use tags, then you have to match the Set method in Bean.

Setting parameters to Bean or fetching parameters from inside will be described in more detail in a later section.

Send data to Bean

Transferring data from an HTML form to Bean requires two tasks:

◆ creates or navigates to Bean with tags

◆ sets attribute values in Bean

* before you create or locate a Bean with a tag, first look up the Bean according to the name you specify. If you can't find it, you will be assigned one. Allows you to create a Bean in one JSP file and then call it in another file, which gives Bean a wide range of running space.

The second step is to set the property value in Bean. The easiest way is to define the value to match the form name. For example, if you define the form name as "username", you define the property "username" in Bean and then use the methods getUsername and setUsername.

Of course, it can also be defined as a different name, as long as you don't think it's troublesome. Who makes you have a good memory?

Request object

The data entered by the user is stored in a Request object and executed with javax.servlet.HttpServletRequest (you can also execute it with other different tools, but they are actually a subset of javax.servlet.HttpServletRequest).

You can also use scriptlet to access Request objects directly. Scriptlet will discuss it in detail in the next lecture, and now all you need to know is that he wrote a piece of code in between in a scripting language. In JSP 1.0, you must use the JavaTM programming language as your scripting language.

You often use the following methods to deal with Request objects:

◆ method

◆ description

◆ execution result

GetRequest

Javax.servlet.jsp.PageContext

Returns the current Request object

GetParameterNames

Javax.servlet.ServletRequest

Returns the current Request object parameter name

GetParameterValues

Javax.servlet.ServletRequest

Returns the current Request object parameter value

You will find that other methods include ServletRequest,HttpServletRequest or any other subset of ServletRequest.

JSP engines often use the Request object after scenes, even if you don't explicitly call it in the JSP file.

Transfer data from Bean to JSP page

Once the user's data is sent to Bean, you want to retrieve the data and display it in the JSP page. To get to this point, you have to use the label. Pass Bean name and attribute name:

< H2 > Hello, < jsp:getProperty name= "mybean" property= "username" / >! < jsp:useBean >, < jsp:setProperty >, and < jsp:getProperty > tags must match, for example: hellouser.jsp: < jsp:useBean id= "mybean" scope= "session" class= "hello.NameHandler" / > < jsp:setProperty name= "mybean" property= "*" / > response.jsp: < H2 > Hello, < jsp:getProperty name= "mybean" property= "username" / >!

In this example, the tag is placed in both files, but the specified name is the same, and if different, the system returns an error message.

How to run the example

I use UNIX host, if you use windows, then change the corresponding path.

Create the path.. / jswdk-1.0/examples/jsp/tutorial/hellouser.

Put the files background.gif, duke.waving.gif, dukebanner.html, hellousr.jsp and response.jsp in it.

Create a directory,.. / jswdk-1.0/examples/WEB-INF/jsp/beans/hello

Put the files NameHandler.java and NameHandler.class in.

Cd../jswdk-1.0 and then startserver.

Open the browser http:// computer name: 8080/examples/jsp/tutorial/hellouser/hellouser.jsp

These are all the contents of the article "how to implement HTML forms in JSP". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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