Struts 2请求映射

Question

I am new in struts and learning it. My question is how struts map request parameter with action instance variable. For Example i have one login form that take username and password. Now it sends request to LoginAction. How this action class will get username in username instance variabel and password in password variable. In servlet we use request.getParameter() method and assign value to particular variable.

Answer 1

in struts2 we use Interceptor , in this case struts2 will set the params for you with param interceptor, you just have to config your interceptor stack (or you just use the default-stack). here is the link to Interceptor , if you are very fresh in struts2, just use the default configuration and take a feel.

example:

<s:form action="my-action">
  <s:textfield name="myField"/>
  <s:submit/>
</s:form>

and

action class:

public class MyActionClass extends ActionSupport{
  private String myField; // getter and setter
  public String execute() throws Exception{
    return "success";
  }
}

configuration:

<package name="default" extends="struts-default">
  <action name="my-action" class="MyActionClass">
    <result>success.jsp</result>
  </action>
</package>

in this case myField will be set automatically by interceptor.

Answer 2

Struts maps the parameters for you. That's part of the reason why using a framework saves you time and effort precisely because you don't have to manually extract parameters from the request .

Struts automatically maps the request parameter username to the username member of your action class by calling setUsername .

See also the struts tutorial

Answer 3

Well Struts2 uses a set of Interceptors which do the heavy lifting for you,this means that at the time of your Action's method execution you will get all the required data to work with.

for transferring data from your JSP to your action class Struts2 use a interceptor name parameters-interceptor , all you need to make property in your action class with the same name as name of the JSP fields and S2 will convert the data and fill the fields for you.

so if you JSP has tow fields with name say userName and password all you need to define thse in your action class with getter and setter like

public class MyAction extends ActionSupport{
  private String userName;
  private String password
  //getter ans setter

 public String execute() throws Exception{
  // do what yoou want
 }


}