p：dataTable rowEdit中的已编辑/更新值在侦听器方法中不可用，因为它们被数据库中的现有数据覆盖

Question

I'm editing data with <p:dataTable> row editor as below.

<p:dataTable value="#{bean.users}" var="user" editable="true">
    <p:ajax event="rowEdit" listener="#{bean.onRowEdit}" />
    <p:ajax event="rowEditCancel" listener="#{bean.onRowEditCancel}" />
    <p:column>
        <p:cellEditor>
            <f:facet name="output">
                <h:outputText value="#{user.firstName}" />
            </f:facet>
            <f:facet name="input">
                <p:inputText value="#{user.firstName}" />
            </f:facet>
        </p:cellEditor>
    </p:column>
</p:dataTable>

The backing bean is implemented as below.

private List<User> users;

@EJB
private UserService userService;

public List<User> getUsers() {
    users = userService.list();
    return users;
}

When I enter the new data in the cellEditor and submit it, they are not available in listener method. I noticed that they get overwritten by the data called from the database.

Why does this happen and how can I avoid it?

Answer 1

Your problem is caused by performing business logic in a getter method. Every iteration over the data table will invoke the getter method. So, while JSF is busy iterating over the data table in order to set the submitted values in the model, the getter calls returns a new list from DB again and again.

You're not supposed to perform business logic in a getter method. As long as you're a starter, you'd better refrain from touching the getter (and setter) methods and perform the job elsewhere in an one time called method.

You likely need a @PostConstruct (and a true service/DAO class) here:

private List<User> users;

@EJB
private UserService userService;

@PostConstruct 
public void init() {
    users = userService.list(); // Call the DB here.
}

public List<User> getUsers() {
    return users; // Just return the already-prepared model. Do NOT do anything else here!
}

See also:

• Why JSF calls getters multiple times