How to pass parameters from Servlet via Bean to JS

问题:

As mentioned below I have made changes to the code which looks like following example, but it doesn't show firstname and lastname in JSP:

Servlet code:

//....
HttpSession session = request.getSession();
Person person = (Person) session.getAttribute("person");
if (person == null) {
    person = new Person();                      
}
person.setNewId(newId);
person.setFirstName(firstName);
person.setLastName(lastName);
session.setAttribute("person", person);

RequestDispatcher rd = request.getRequestDispatcher("jsp Address");
rd.forward(request, response);

Person Bean code:

private int newId;
private String firstName;
private String lastName;

// Default Constructor
public Person() {}

public Person(int newId, String firstName, String lastName) {
    setNewId(newId);
    setFirstName(firstName);
    setLastName(lastName);
}

//Getter and Setter Methods
public int getNewId() {return newId;}
public void setNewId(int newID) {this.newId = newID;}
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;}

And in JSP code:

<jsp:useBean id="person" type="app.models.Person" scope="session">
    <jsp:getProperty name="person" property="firstName" />
    <jsp:getProperty name="person" property="lastName" />
</jsp:useBean>

Output of this JSP page: none

Expected output: firstName lastName

Questions:

1. How can i pass parameters from Servlets to JSP via Bean with help of Session? 
2. Is there a better way to do this code? I am using MVC architecture.

回答1:

Get rid of the <jsp:useBean>. When using the type attribute instead of class, it won't check if there's already an instance in the scope, it will plain override the Person instance which you created in the servlet with a new, blank, default constructed instance.

When using "MVC architecture", the <jsp:useBean> tag is useless. Remove it and just use usual EL to access it:

${person.firstName} ${person.lastName}

Or better, to prevent XSS attacks, use JSTL <c:out>.

<c:out value="${person.firstName} ${person.lastName}" />