| This tutorial assumes you've completed the Coding Struts 2 Actons tutorial and have a working Coding_Actions_Struts2_Ant (or Coding_Actions_Struts2_Mvn) project. The example code for this tutorial, Form_Processing_Struts2_Ant or Form_Processing_Struts2_Mvn, is available on Google Code - http://code.google.com/p/struts2-examples/downloads/list. After downloading and unzipping the file, you'll have a folder named Form_Processing_Struts2_Ant (or Form_Processing_Struts2_Mvn). In that folder will be a README.txt file with instructions on now to build and run the example application. |
Introduction
In this tutorial we'll explore using Struts 2 to do more involved processing of a form submission. We'll cover how to use a Java model class to store the form input and how to create the Struts 2 form to match up with that model class.
在这个示例中，将会展示更多的表单提交的过程，将会介绍怎么使用一个model java 类去存储表单提交过来的是数据，以及怎样创建一个表单与这个model类相匹配。
The code provided in this tutorial may be added to the
Coding Struts 2 Actions example or you can download this complete example from Google Code -
http://code.google.com/p/struts2-examples/downloads/list.
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The Struts 2 user mailing list is an excellent place to get help. If you are having a problem getting the tutorial example applications to work search the Struts 2 mailing list. If you don't find an answer to your problem, post a question on the mailing list. |
Forms and A Java Model Class
For this tutorial let's say we need to provide a form that a user may submit to register for a prize drawing. Our business rules state the user must provide his/her first name, last name, email address, and age.
To encapsulate this data, we'll use a simple Java class that follows the basic Java Bean specifications (public set/get methods for each instance field). If you're following along add this class to package org.apache.struts.register.model in the
Coding Struts 2 Actions example.
下面是一个java bean,有一些属性和必要的公有set,get 方法。
public class Person { private String firstName; private String lastName; private String email; private int age; public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public int getAge() { return age; } public void setAge( int age) { this.age = age; } public String toString() { return "First Name: " + getFirstName() + " Last Name: " + getLastName() + " Email: " + getEmail() + " Age: " + getAge() ; } }
Note a few points about the above class. There is a public set/get method for each instance field. The age attribute is of type integer. We've defined a public toString method that returns a String representing the state of the object. Since we haven't specified
a constructor, Java will provide a default constructor that will set all instance fields to their null values.
注意，上面的java bean ,为每一个属性都供了公有的set,get方法，因为age属性是整型的，所以，定义了一个公有的toString方法，用来返回一个字符串。由于没有自定义构造方法，所以默认构造方法会为这些属性赋上空值。
Form Structure
To collect the above information we'll use a Struts 2 form. When creating this form the key concept we need to employ is to tie each form field to a specific instance field of an object of type Person. Let's look over the form first and then discuss some
key points. Create a view page named register.jsp (in WebContent (Ant version) or src/main/webapp (Maven version) )
为了接收上面的信息，我们使用struts2表单标签，这时，需要和上面java bean定义的属性相对应。
<?xml version="1.0" encoding="ISO-8859-1" ?> <%@ taglib prefix="s" uri="/struts-tags" %> <%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /> <title>Register</title> </head> <body> <h3>Register for a prize by completing this form.</h3> <s:form action="register"> <s:textfield name="personBean.firstName" label="First name" /> <s:textfield name="personBean.lastName" label="Last name" /> <s:textfield name="personBean.email" label ="Email"/> <s:textfield name="personBean.age" label="Age" /> <s:submit/> </s:form> </body> </html>
Since we are using Struts 2 tags, at the top of the page we need the Struts tag library declaration.
我们使用了标签，所以需要声明标签库
The Struts 2 form will submit to an action named register. We'll need to define that action in our struts.xml file.
接下来我们需要在struts.xml定义这个action
Note the four Struts 2 textfield tags. Each tag has a name value that includes an attribute of the Person class (e.g. firstName). The name attribute's value also has a reference to an object called personBean. This object is of type Person. When we create
the Action class that handles this form submission, we'll have to specify that object in that Action class (see below).
The complete name value, personBean.firstName, instructs Struts 2 to use the input value for that textfield as the argument to the personBean object's setFirstName method. So if the user types "Bruce" in the textfield that has the label "First name", the
personBean's firstName instance field will have a value of "Bruce".
Note we have a Struts 2 textfield for each instance field of the class Person.
Remember that Person class's age attribute is of type integer. All form field input values are Strings.
Struts 2 will automatically convert the String value ("25") the user entered for the age form field to 25
when calling the setAge method of object personBean.
注意，age属性是整型的，struts2会自动将字符型转化成整型。
Creating the Action Class To Handle the Form Submission
When the user clicks on the submit button of the above form, the action "register" and the form data will be sent to the Struts 2 framework. We need an Action class to process this form. If you recall from the tutorial
Coding Struts 2 Actions our Action class should extends the Struts 2 ActionSupport class.
Here is the Action class used for this example. Place it in package org.apache.struts.register.action.
下面是一个action类，在参数传递上（有三种方式，请参考我的博文），使用了demoModel，
package org.apache.struts.register.action; import org.apache.struts.register.model.Person; import com.opensymphony.xwork2.ActionSupport; public class Register extends ActionSupport { private static final long serialVersionUID = 1L; private Person personBean; @Override public String execute() throws Exception { //call Service class to store personBean's state in database return SUCCESS; } public Person getPersonBean() { return personBean; } public void setPersonBean(Person person) { personBean = person; } }
In the Register class note that we've declared an attribute named personBean of type Person and there is a public get and set method for this object.
请注意上面用红色标注的属性。
The Register class also overrides the execute method. The execute method is the one we will specify in the struts.xml to be called in response to the register action. In this example, the execute method just returns the String constant SUCCESS (inherited
from ActionSupport class). But in a real application, within the execute method we would call upon other classes (Service objects) to perform the business processing of the form, such as storing the user's input into a data repository.
上面的类重写了execute方法，这个方法是在struts.xml指定的。这个示例中，该方法只是返回一个success.但是在一个真正的应用中，在该方法我们将会调用其他类来实现一些业务流程。
The personBean object of type Person declared in the Register Action class matches the personBean name we used in the form's textfields. When the form is submitted, the Struts 2 framework will inspect the Action class and look for an object named personBean.
It will create that object using the Person class's default constructor. Then for each form field that has a name value of personBean.someAttribute (e.g personBean.firstName) it will call the personBean's public set method for that attribute and pass it the
form field's value (the user input). This all happens before the execute method occurs.
在这个action类中声明的personBean对象与我们在表单中名字相匹配，但提交表单后，struts2框架将会检查action 类，然后寻找名为personBean的对象，会通过默认构造函数创建这个对象。这个对象对调用公有set方法把那些属性值赋给属性，这些都发生在exectue执行之前。
When Struts 2 runs the execute method of class Register, the personBean object in class Register now has values for its instance fields that are equal to the values the user entered into the corresponding form fields.
By using a Java model class to encapsulate the data provided by the form we don't have to have a separate attribute (with public set/get methods) in the Action class (Register) for each form field.
Handle SUCCESS Being Returned By Execute Method
When SUCCESS is returned by the execute method we want to display a simple thank you page that shows the user's registration. Add the thankyou.jsp below to either WebContent (Ant) or src/main/webapp (Maven).
<?xml version="1.0" encoding="ISO-8859-1" ?> <%@ taglib prefix="s" uri="/struts-tags" %> <%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /> <title>Registration Successful</title> </head> <body> <h3>Thank you for registering for a prize.</h3> <p>Your registration information: <s:property value="personBean" /> </p> <p><a href="<s:url action='index' />" >Return to home page</a>.</p> </body> </html>
If you don't recall how the Struts 2 property and url tags work consult the
Using Struts 2 Tags tutorial.
Create action Node In struts.xml
To specify the relationship between the form submission page, the Struts 2 Action class, and the success view page we need to add an action node to struts.xml. Add this action node to struts.xml (src folder (Ant version) or src/main/resources (Maven version)
) after the hello action and before the closing package node.
<action name="register" class="org.apache.struts.register.action.Register" method="execute"> <result name="success">/thankyou.jsp</result> </action>
The above action tells Struts 2 that when the register action is provided to call method execute of class Register. If that method returns result "success" return to the browser the thankyou.jsp.
Note that we don't need to tell Struts 2 anything about processing the form. The transfer of the form field input values to the personBean object will happen automatically provided we've followed the convention of naming our form fields to match personBean.attributeName
(e.g. personBean.lastName).
Create A Link To register.jsp
So that the user can find the registration page, add this link to index.jsp
<p><a href="register.jsp">Please register</a> for our prize drawing.</p>
Run The Example
If everything is correct, you should be able to create the war file (ant archive or mvn package), deploy the war file to your Servlet container, and open this URL in your web browser:
http://localhost:8080/Form_Processing_Struts2_Ant/index.action (Ant version) or
http://localhost:8080/Form_Processing_Struts2_Mvn/index.action (Maven version). On that page should be a link to register. Click on that link and you should see the register.jsp page.
Fill out the form and click the submit button. You should then see the thankyou.jsp page.
In our next tutorial we'll cover how to validate the user's input in the form.