[6] Learn Struts and Form-related labels

xiaoxiao2021-03-06 102

Continue to learn the HTML tag library provided by Struts.

BY Budi Kurniawan

In the first part of this series, I tells how to use the HTML tag library provided by Struts to configure a Struts application. I also introduced a class of labels in the label library: a label that uses independently. In the second part I will continue to introduce the second type of label: Tags related to Form.

Tags related to the Form include the

tag itself, and all the labels that must be included there. For example, the and tags are related to Form, because if they don't put them in a form, they don't make sense.

Tags tag is used to generate an HTML Form. Many rules must be followed when using this tag.

First, an action property must be included in the tag, which is the only necessary attribute in this tab. If this property does not have this attribute, the JSP page will throw an exception. You must give this Action property to a valid value. A valid value refers to the access path of any child element in the element in the application's Struts configuration file. Moreover, there must be a Name property in the corresponding element, which is the name of the Form Bean.

For example, if you have such a tag:

Then there must be a element that is displayed as a bold in the element of your Struts profile:

TYPE = "com.javapro.struts.loginaction"

Name = "loginform"

Scope = "request"

INPUT = "/ login.jsp">

That is to say that a FORM tag is associated with form beans.

Another rule to follow is: any label (, , , , <radio>, <checkbox>, <select>, <checkbox>, <select>, <Checkbox>, <SELECT>, <CheckBox>, <SELECT> ) Must have a specified attribute value in the relevant Form Bean. For example, if you have an attribute value being specified as "username" <text> tag, the relevant form bean must also have an attribute called "UserName". Enter the value in the <TEXT> tab being used to generate the FORM BEAN's UserName property.</p> <p>In addition to the properties mentioned above, the <form> tag has some attributes that are not necessarily, but better "secondary". For example, you can generate JavaScript with a FOCUS property, which will "Focus" to the form of the Form on an element included. You need to specify the name of the element when you use the FOCUS properties. For example, the following code is fixed on the second Text element:</p> <p><body></p> <p><html: form action = "/ login" FOCUS = "password"> user name: <html: text proteth = "username" /></p> <p><br> Password: <html: Text Property = "Password" /></p> <p><br> <HTML: Submit /></p> <p></ html: form></p> <p></ body></p> <p>This segment code will be converted to:</p> <p><body></p> <p><form name = "loginform" Method = "POST"</p> <p>Action = "/ mystrutsapp6 / login.do"></p> <p>User name: <input type = "text" Name = "username"</p> <p>Value = ""></p> <p><br> Password: <input type = "text"</p> <p>Name = "Password" value = ">"></p> <p><br> <input type = "submit"</p> <p>Value = "Submit"></p> <p></ form></p> <p><script language = "javascript"</p> <p>TYPE = "text / javascript"></p> <p><! -</p> <p>IF (Document.Forms ["LoginForm"]. Elements [</p> <p>"Password"]. Type! = "hidden")</p> <p>Document.Forms ["Loginform"]. Elements [</p> <p>"password"]. FOCUS ()</p> <p>// -></p> <p></ script></p> <p></ body></p> <p>Note that the default value of the method attribute in the <form> tag is POST. In addition, have you seen this tag library how to build JavaScript to set the focus to the Password element? This is also one of the people who are fascinating. You don't have to worry about how to program on the client, it will help you generate.</p> <p>Pay attention to the example of running the previous example, you have to have a related Form containing the username and password properties. You can refer to the Login program in the third part of this article.</p> <p><text> Tags <text> tag is used to generate a text's input area. It must contain the "Property" attribute corresponding to the same properties in the related Form bean. This tag is only valid when embedded in a <form> tag.</p> <p>E.g:</p> <p><HTML: Text Property = "UserName" /></p> <p>Will be converted to:</p> <p><Input Type = "text" name = "username" value = ">></p> <p><Password> Tags <Password> Tags are used to generate an input area of type password. It must contain the "Property" attribute corresponding to the same properties in the related Form bean. This tag is only valid when embedded in a <form> tag. One of the important properties in this tag is "redisplay", which is used to redisplay the value previously entered into this area. The default value of this property is TRUE. However, in order to make Password can't be redisplay, you may want to set the value of this property to false. E.g:</p> <p><html: Password property = "password"</p> <p>REDISPLAY = "false" /></p> <p>Will be converted to:</p> <p><Input Type = "Password" name = "password"</p> <p>Value = ""></p> <p><Hidden> Tag <Hidden> Tag is used to generate an input area hidden text. It must contain the "Property" attribute corresponding to the same properties in the related Form bean. This tag is only valid when embedded in a <form> tag:</p> <p>E.g:</p> <p><html: hidden property = "usrname" /></p> <p>Will be converted to:</p> <p><Input Type = "Hidden" Name = "UserName" Value = ">></p> <p><textarea> Tags <textarea> Tags are used to generate a text area element (Text Area Element). It must contain the "Property" attribute corresponding to the same properties in the related Form bean.</p> <p>such as:</p> <p><html: Textarea Property = "Details"</p> <p>COLS = "80"</p> <p>ROWS = "20"</p> <p>Value = "Enter Details Here" /></p> <p>Will be converted to:</p> <p><textarea name = "details" cols = "80"</p> <p>Rows = "20"> Enter Details Here </ textarea></p> <p><RADIO> Tag <RADIO> Tag is used to display a radio button. It must contain "value" attributes. For example, this code:</p> <p><html: Radio Property = "Title" value = "1" /> mr.</p> <p><html: Radio Property = "Title" value = "2" /> ms.</p> <p><html: Radio Property = "Title" value = "3" /> DR.</p> <p>Will be converted into such an HTML:</p> <p><Input Type = "Radio" name = "Title"</p> <p>Value = "1"> MR.</p> <p><Input Type = "Radio" name = "Title"</p> <p>Value = "2"> ms.</p> <p><Input Type = "Radio" name = "title" value = "3"> DR.</p> <p><CheckBox> Tags <CheckBox> Tags are used to display the input area of the Checkbox type. such as:</p> <p><html: checkbox property =</p> <p>"notify" /> please send me notification</p> <p>Will be converted to:</p> <p><Input Type = "Checkbox" name = "notify"</p> <p>Value = "on"> please send me notification</p> <p><Submit> Tags <Submit> tag is used to generate the input area of the submitted type. such as:</p> <p><html: Submit value = "login" /></p> <p>Will be converted to:</p> <p><Input Type = "Submit" Value = "Login"></p> <p><RESET> Tags <RESET> Tags are used to generate the input area of the Type Reset. such as:</p> <p><html: reset /></p> <p>Will be converted to:</p> <p><Input Type = "RESET" value = "reset"></p> <p><Option> Tags <option> Tags are used to display an option in Select Box. Refer to the <SELECT> tags below.</p> <p><SELECT> Tags <SELECT> tab is used to display an HTML selection element containing zero or more options. It must be embedded in a <form> tag that is valid. The following example will explain how to use this tag:</p> <p><html: select property = "color" size = "3"></p> <p><html: option value =</p> <p>"r"> red </ html: option></p> <p><html: option value =</p> <p>"g"> Green </ html: option></p> <p><html: option value =</p> <p>"B"> Blue </ html: option></p> <p></ html: select></p> <p>Will be converted to:</p> <p><select name = "color" size = "3"> <option</p> <p>Value = "r"> Red </ option></p> <p><option value = "g"> Green </ option></p> <p><option value = "b"> blue </ option></p> <p></ select></p> <p>In the second part of this series, you have learned some more important and form-related labels. Before using these tags, you must use some rules to use them correctly. The third part will tell how these labels are used in a real program.</p> <p>About the Author:</p> <p>Budi Kurniawan is an IT consultant that he specializes in Internet and object-oriented programming, teaches Java and Microsoft technology. He is very good</p> <p>Java for the web with servlets, jsp, and ejb; a developer's Guide To Scalable Solutions (New Riders) Author, he also developed the most popular Java Upload Bean, you can get it from Brainysoftware.com, many important Companies are licensed and used in the project. 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