First Step: write the JavaBean source code.
package register.test;
import java.util.Map;
import java.util.HashMap;
public class RegisterBean {
private String name;
private String age;
private String email;
private Map<String,String> errors;
public RegisterBean() {
this.name="";
this.age="";
this.email="";
this.errors=new HashMap<String,String>();
}
public boolean isValid() {
boolean flag = true ;
if(!this.name.matches("\\w{6,15}")){
flag = false ;
this.name = "" ;
this.errors.put("errname","user name must between 6~15 words") ;
}
if(!this.email.matches("\\w+@\\w+\\.\\w+\\.?\\w*")){
flag = false ;
this.email = "" ;
this.errors.put("erremail","Email doesn't match.") ;
}
if(!this.age.matches("\\d+")){
flag = false ;
this.age = "" ;
this.errors.put("errage","Age must be a number") ;
}
return flag ;
}
public String getError(String key) {
String value=this.errors.get(key);
return value==null?"":value;
}
public void setName(String name) {
this.name=name;
}
public void setAge(String age) {
this.age=age;
}
public void setEmail(String email) {
this.email=email;
}
public String getName() {
return name;
}
public String getAge() {
return age;
}
public String getEmail() {
return email;
}
}Then We should have a register page, here we go:
<html>
<head>
<title>Register Page</title>
</head>
<jsp:useBean id="user" scope="request" class="register.test.RegisterBean"/>
<body>
<form action="check.jsp" method="post">
Account ID: <input type="text" name="name" value="<jsp:getProperty name="user" property="name"/>"/><%=user.getError("errname")%><br>
Age : <input type="text" name="age" value="<jsp:getProperty name="user" property="age"/>"/><%=user.getError("errage")%><br>
Email: <input type="text" name="email" value="<jsp:getProperty name="user" property="email"/>"/><%=user.getError("erremail")%><br>
<input type="submit" value="Submit">
</form>
</body>
</html>When we submit this form, we use check.jsp to check the form content.
<html>
<head>
<title>Check Page</title>
</head>
<body>
<jsp:useBean id="user" scope="request" class="register.test.RegisterBean"/>
<jsp:setProperty name="user" property="*"/>
<% if (user.isValid()) {%>
<jsp:forward page="show.htm"/>
<%} else {%>
<jsp:forward page="index1.jsp"/>
<%}%>
</body>
</html>Here we omit the show page, it's not important.
*we should notice something here
->we should use the label to setProperty for the instance of a JavaBean, it will never be done automatically.
->when we need some data from the JavaBean, we use getProperty and if we need to modify the data, we must use setProperty label manually.