In the Using Tags lesson, we implemented a Logon form. In the Coding Actions lesson, we interpret the Logon form, and return a different result code depending on the circumstances.
If you have coded along, you can open the Logon action
http://localhost:8080/tutorial/Logon.action
and enter a likely username and password. Since we haven't given the Action any behavior, the mapping redisplays the default Logon.jsp
page.
Let's add an Action class that will make the Logon form more interesting.
The Code
Just as an example, we can examine the username and password values. If either or both properties are empty, return INPUT, so that we can collect a valid Logon. Otherwise, return SUCCESS.
package tutorial; import com.opensymphony.xwork2.ActionSupport; public class Logon extends ActionSupport { public String execute() throws Exception { if (isInvalid(getUsername())) return INPUT; if (isInvalid(getPassword())) return INPUT; return SUCCESS; } private boolean isInvalid(String value) { return (value == null || value.length() == 0); } private String username; public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } private String password; public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } }
How The Code Works
The framework automatically populates the username and password properties for us. All that's left to do is checking to see if either property is empty.
What to Remember
The Actions do the "heavy lifting" in a web application. Actions interact with data base systems and business rule engines, so that we can turn "billboard" HTML into a rich, dynamic web experience.
After doing its work, an Action returns a result code to indicate what the framework should do next. Often, the next step is to go onto the "success" result. Other times, we might need to go to an "error" result instead. In either case, the Action does not worry about generating the response, only deciding which logical result to present next.
For more about Actions, see Big Picture in the Core Developers Guide.
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5 Comments
Unknown User (victorsosa)
OK Where are these examples?
Ted Husted
> OK Where are these examples?
By "examples", I think Victor is referring to examples of using check boxes and radio buttons and such using a parameter map. In an earlier revision, there were references to there being examples of using these elements in another lesson.
Anton Pussep
1. Typo: write "password" instead of "passowrd" (somewhere on the top in the introduction).
2. The "prev" link should go to the "Using Tags" page instead of the "Hello World" page.
Dave Newton
Fixed; thanks for the feedback.
David Durham
I think this example, and the previous ones, would be better if they contained the JSP fragments, Action code, and Action mapping XML snippets. While this page is focused primarily on an Action class, the JSP fragments and Action mapping XML provide needed context for someone getting started with Struts. Basically, they won't have to navigate between this and previous pages in order to get a bigger picture of what's happening here.