Jsf 为什么使用同一个变量<；p：选择布尔复选框/>；抛出NPE，同时<；h：选择布尔复选框/>；不'；T

我有下一个代码片段，它与

的预期效果一样，如果我使用

，它将失败：

变量、它们的值、方法等都是可以的，所以我想没有必要提供它的代码，但是如果您愿意，您可以检查我前面的问题，以获得所有必要代码的更多细节

所以，问题是：为什么在同一个变量上

抛出NPE，而

不抛出NPE？如何解决这个问题？我想使用PrimeFaces组件

谢谢大家!

//编辑

HomeBean.java：

import com.infostroy.adminportal.bean.BaseBean;
import com.infostroy.adminportal.model.Application;
import com.infostroy.adminportal.model.Computer;
import com.infostroy.adminportal.model.User;
import java.io.IOException;
import java.security.NoSuchAlgorithmException;
import java.util.List;
import javax.annotation.PostConstruct;
import org.primefaces.context.RequestContext;
import org.primefaces.event.SelectEvent;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;

@Component
@Scope("session")
public class HomeBean extends BaseBean {

    private static final String editUserBtn = "tab:form1:editUser";
    private static final String deleteUserBtn = "tab:form1:deleteUser";
    private static final String editCompBtn = "tab:form2:editComp";
    private static final String deleteCompBtn = "tab:form2:deleteComp";
    private static final String editAppBtn = "tab:form3:editApp";
    private static final String deleteAppBtn = "tab:form3:deleteApp";

    private List<User> users;
    private List<Computer> computers;
    private List<Application> applications;
    private User selectedUser, newUser;
    private Computer selectedComputer, newComputer;
    private Application selectedApplication, newApplication;
    private String deleteUserMsg, deleteCompMsg, deleteAppMsg;
    private RequestContext rc;

    @PostConstruct
    public void init() {
        setUsers(hibernateDBManager.getAllUsers());
        setComputers(hibernateDBManager.getAllComputers());
        setApplications(hibernateDBManager.getAllApplications());
        newUser = new User();
        newComputer = new Computer();
        newApplication = new Application();
        rc = RequestContext.getCurrentInstance();
    }

    public void addUser() throws NoSuchAlgorithmException {
        if (hibernateDBManager.insertUser(newUser)) {
            users.add(newUser);
            newUser = new User();
            updateUserButtons();
        }
    }

    public void editUser() throws NoSuchAlgorithmException {
        if (hibernateDBManager.updateUser(selectedUser)) {
            users.set(users.indexOf(selectedUser), selectedUser);
            selectedUser = null;
            updateUserButtons();
        }
    }

    public void deleteUser() throws IOException {
        if (selectedUser != null) {
            if (hibernateDBManager.deleteUserById(selectedUser.getUserId()) > 0) {
                users.remove(selectedUser);
                selectedUser = null;
                updateUserButtons();
            }
        }
    }

    public void addComputer() {
        if (newComputer != null && hibernateDBManager.insertComputer(newComputer)) {
            computers.add(newComputer);
            newComputer = new Computer();
            updateCompButtons();
        }
    }

    public void editComputer() {
        if (hibernateDBManager.updateComputer(selectedComputer)) {
            computers.set(computers.indexOf(selectedComputer), selectedComputer);
            selectedComputer = null;
            updateCompButtons();
        }
    }

    public void deleteComputer() {
        if (selectedComputer != null) {
            if (hibernateDBManager.deleteComputerById(selectedComputer.getComputerId()) > 0) {
                computers.remove(selectedComputer);
                selectedComputer = null;
                updateCompButtons();
            }
        }
    }

    public void addApplication() {
        if (newApplication != null && hibernateDBManager.insertApplication(newApplication)) {
            applications.add(newApplication);
            newApplication = new Application();
            updateAppButtons();
        }
    }

    public void editApplication() {
        if (hibernateDBManager.updateApplication(selectedApplication)) {
            applications.set(applications.indexOf(selectedApplication), selectedApplication);
            selectedApplication = null;
            updateAppButtons();
        } 
    }

    public void deleteApplication() {
        if (selectedApplication != null) {
            if (hibernateDBManager.deleteApplicationById(selectedApplication.getAppId()) > 0) {
                applications.remove(selectedApplication);
                selectedApplication = null;
                updateAppButtons();
            }
        }
    }

    public void onUserRowSelect(SelectEvent event) {
        setSelectedUser((User) event.getObject());
        setDeleteUserMsg("Are you sure you want to delete user "
                + selectedUser.getFirstName() + " " + selectedUser.getLastName() + "?");
    }

    public void onCompRowSelect(SelectEvent event) {
        setSelectedComputer((Computer) event.getObject());
        deleteCompMsg = "Are you sure you want to delete computer "
                + selectedComputer.getComputerName()
                + " (" + selectedComputer.getIpAddress() + ") ?";
    }

    public void onAppRowSelect(SelectEvent event) {
        setSelectedApplication((Application) event.getObject());
        deleteAppMsg = "Are you sure you want to delete application "
                + selectedApplication.getAppName() + "?";
    }

    protected void updateUserButtons() {
        rc.update(editUserBtn);
        rc.update(deleteUserBtn);
    }

    protected void updateCompButtons() {
        rc.update(editCompBtn);
        rc.update(deleteCompBtn);
    }

    protected void updateAppButtons() {
        rc.update(editAppBtn);
        rc.update(deleteAppBtn);
    }

    public String getDeleteUserMsg() {
        return deleteUserMsg;
    }

    public void setDeleteUserMsg(String deleteUserMsg) {
        this.deleteUserMsg = deleteUserMsg;
    }

    public String getDeleteCompMsg() {
        return deleteCompMsg;
    }

    public void setDeleteCompMsg(String deleteCompMsg) {
        this.deleteCompMsg = deleteCompMsg;
    }

    public String getDeleteAppMsg() {
        return deleteAppMsg;
    }

    public void setDeleteAppMsg(String deleteAppMsg) {
        this.deleteAppMsg = deleteAppMsg;
    }
    //Other getters/setters

}

import com.infostroy.adminportal.bean.BaseBean；
导入com.infostroy.adminportal.model.Application；
导入com.infostroy.adminportal.model.Computer；
导入com.infostroy.adminportal.model.User；
导入java.io.IOException；
导入java.security.NoSuchAlgorithmException；
导入java.util.List；
导入javax.annotation.PostConstruct；
导入org.primefaces.context.RequestContext；
导入org.primefaces.event.SelectEvent；
导入org.springframework.context.annotation.Scope；
导入org.springframework.stereotype.Component；
@组成部分
@范围（“会议”）
公共类HomeBean扩展了BaseBean{
私有静态最终字符串editUserBtn=“tab:form1:editUser”；
私有静态最终字符串deleteUserBtn=“tab:form1:deleteUser”；
私有静态最终字符串editCompBtn=“tab:form2:editComp”；
私有静态最终字符串deleteCompBtn=“tab:form2:deleteComp”；
私有静态最终字符串editAppBtn=“tab:form3:editApp”；
私有静态最终字符串deleteAppBtn=“tab:form3:deleteApp”；
私人名单用户；
私人名单计算机；
私人名单申请；
私人用户选择用户，新用户；
私人电脑选择电脑，新电脑；
私有应用程序选择应用程序、新应用程序；
私有字符串deleteUserMsg、deleteCompMsg、deleteAppMsg；
私有请求上下文rc；
@施工后
公共void init（）{
setUsers（hibernateDBManager.getAllUsers（））；
setComputers（hibernateDBManager.getAllComputers（））；
setApplications（hibernateDBManager.getAllApplications（））；
newUser=newUser（）；
新计算机=新计算机（）；
newApplication=newApplication（）；
rc=RequestContext.getCurrentInstance（）；
}
public void addUser（）引发NoSuchAlgorithmException{
if（休眠的bmanager.insertUser（新用户））{
users.add（newUser）；
newUser=newUser（）；
updateUserButtons（）；
}
}
public void editUser（）引发NoSuchAlgorithmException{
if（hibernateDBManager.updateUser（selectedUser））{
users.set（users.indexOf（selectedUser），selectedUser）；
selectedUser=null；
updateUserButtons（）；
}
}
public void deleteUser（）引发IOException{
如果（selectedUser！=null）{
如果（hibernateDBManager.deleteUserById（selectedUser.getUserId（））>0）{
用户。删除（选择用户）；
selectedUser=null；
updateUserButtons（）；
}
}
}
公共计算机（）{
if（newComputer！=null&&hibernateDBManager.insertComputer（newComputer））{
计算机。添加（新计算机）；
新计算机=新计算机（）；
updateCompButtons（）；
}
}
公共计算机（）{
如果（hibernateDBManager.updateComputer（selectedComputer））{
computers.set（computers.indexOf（selectedComputer），selectedComputer）；
selectedComputer=null；
updateCompButtons（）；
}
}
公共计算机（）{
如果（selectedComputer！=null）{
如果（hibernateDBManager.deleteComputerById（selectedComputer.getComputerId（））>0）{
计算机。删除（所选计算机）；
selectedComputer=null；
updateCompButtons（）；
}
}
}
公共应用程序（）{
if（newApplication！=null&&hibernateDBManager.insertApplication（newApplication））{
应用程序。添加（新应用程序）；
newApplication=newApplication（）；
updateAppButtons（）；
}
}
公共应用程序（）{
if（hibernateDBManager.updateApplication（selectedApplication））{
applications.set（applications.indexOf（selectedApplication），selectedApplication）；
selectedApplication=null；
updateAppButtons（）；
} 
}
公共应用程序（）{
如果（selectedApplication！=空）{
如果（hibernateDBManager.deleteApplicationById（selectedApplication.getAppId（））>0）{
应用程序。删除（选定的应用程序）；
selectedApplication=null；
updateAppButtons（）；
}
}
}
公共无效onUserRowSelect（SelectEvent事件）{
setSelectedUser（（用户）event.getObject（））；
setDeleteUserMsg（“您确定要删除用户吗？”
+selectedUser.getFirstName（）+“”+selectedUser.getLastName（）+“？”；
}
public void onCompRowSelect（SelectEvent事件）{
setSelectedComputer（（计算机）事件.getObject（））；
deleteCompMsg=“是否确实要删除计算机？”
+selectedComputer.getComputerName（）
+（“+selectedComputer.getIpAddress（）+”）；
}
Approwselect上的公共无效（SelectEvent事件）{
setSelectedApplication（（应用程序）event.getObject（））；
deleteAppMsg=“是否确实要删除应用程序？”
+selectedApplication.getAppName（）+“？”；
}
受保护的void updateUserButtons（）{
rc.update（editUserBtn）；
rc.update（deleteUserBtn）；
}
受保护的void updateCompButtons（）{
rc.更新（editCompBtn）；
rc.更新（删除compbt）
/pages/home.xhtml @424,149 value="#{homeBean.selectedApplication.licenseRequired}": Target Unreachable, 'selectedApplication' returned null

import com.infostroy.adminportal.bean.BaseBean;
import com.infostroy.adminportal.model.Application;
import com.infostroy.adminportal.model.Computer;
import com.infostroy.adminportal.model.User;
import java.io.IOException;
import java.security.NoSuchAlgorithmException;
import java.util.List;
import javax.annotation.PostConstruct;
import org.primefaces.context.RequestContext;
import org.primefaces.event.SelectEvent;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;

@Component
@Scope("session")
public class HomeBean extends BaseBean {

    private static final String editUserBtn = "tab:form1:editUser";
    private static final String deleteUserBtn = "tab:form1:deleteUser";
    private static final String editCompBtn = "tab:form2:editComp";
    private static final String deleteCompBtn = "tab:form2:deleteComp";
    private static final String editAppBtn = "tab:form3:editApp";
    private static final String deleteAppBtn = "tab:form3:deleteApp";

    private List<User> users;
    private List<Computer> computers;
    private List<Application> applications;
    private User selectedUser, newUser;
    private Computer selectedComputer, newComputer;
    private Application selectedApplication, newApplication;
    private String deleteUserMsg, deleteCompMsg, deleteAppMsg;
    private RequestContext rc;

    @PostConstruct
    public void init() {
        setUsers(hibernateDBManager.getAllUsers());
        setComputers(hibernateDBManager.getAllComputers());
        setApplications(hibernateDBManager.getAllApplications());
        newUser = new User();
        newComputer = new Computer();
        newApplication = new Application();
        rc = RequestContext.getCurrentInstance();
    }

    public void addUser() throws NoSuchAlgorithmException {
        if (hibernateDBManager.insertUser(newUser)) {
            users.add(newUser);
            newUser = new User();
            updateUserButtons();
        }
    }

    public void editUser() throws NoSuchAlgorithmException {
        if (hibernateDBManager.updateUser(selectedUser)) {
            users.set(users.indexOf(selectedUser), selectedUser);
            selectedUser = null;
            updateUserButtons();
        }
    }

    public void deleteUser() throws IOException {
        if (selectedUser != null) {
            if (hibernateDBManager.deleteUserById(selectedUser.getUserId()) > 0) {
                users.remove(selectedUser);
                selectedUser = null;
                updateUserButtons();
            }
        }
    }

    public void addComputer() {
        if (newComputer != null && hibernateDBManager.insertComputer(newComputer)) {
            computers.add(newComputer);
            newComputer = new Computer();
            updateCompButtons();
        }
    }

    public void editComputer() {
        if (hibernateDBManager.updateComputer(selectedComputer)) {
            computers.set(computers.indexOf(selectedComputer), selectedComputer);
            selectedComputer = null;
            updateCompButtons();
        }
    }

    public void deleteComputer() {
        if (selectedComputer != null) {
            if (hibernateDBManager.deleteComputerById(selectedComputer.getComputerId()) > 0) {
                computers.remove(selectedComputer);
                selectedComputer = null;
                updateCompButtons();
            }
        }
    }

    public void addApplication() {
        if (newApplication != null && hibernateDBManager.insertApplication(newApplication)) {
            applications.add(newApplication);
            newApplication = new Application();
            updateAppButtons();
        }
    }

    public void editApplication() {
        if (hibernateDBManager.updateApplication(selectedApplication)) {
            applications.set(applications.indexOf(selectedApplication), selectedApplication);
            selectedApplication = null;
            updateAppButtons();
        } 
    }

    public void deleteApplication() {
        if (selectedApplication != null) {
            if (hibernateDBManager.deleteApplicationById(selectedApplication.getAppId()) > 0) {
                applications.remove(selectedApplication);
                selectedApplication = null;
                updateAppButtons();
            }
        }
    }

    public void onUserRowSelect(SelectEvent event) {
        setSelectedUser((User) event.getObject());
        setDeleteUserMsg("Are you sure you want to delete user "
                + selectedUser.getFirstName() + " " + selectedUser.getLastName() + "?");
    }

    public void onCompRowSelect(SelectEvent event) {
        setSelectedComputer((Computer) event.getObject());
        deleteCompMsg = "Are you sure you want to delete computer "
                + selectedComputer.getComputerName()
                + " (" + selectedComputer.getIpAddress() + ") ?";
    }

    public void onAppRowSelect(SelectEvent event) {
        setSelectedApplication((Application) event.getObject());
        deleteAppMsg = "Are you sure you want to delete application "
                + selectedApplication.getAppName() + "?";
    }

    protected void updateUserButtons() {
        rc.update(editUserBtn);
        rc.update(deleteUserBtn);
    }

    protected void updateCompButtons() {
        rc.update(editCompBtn);
        rc.update(deleteCompBtn);
    }

    protected void updateAppButtons() {
        rc.update(editAppBtn);
        rc.update(deleteAppBtn);
    }

    public String getDeleteUserMsg() {
        return deleteUserMsg;
    }

    public void setDeleteUserMsg(String deleteUserMsg) {
        this.deleteUserMsg = deleteUserMsg;
    }

    public String getDeleteCompMsg() {
        return deleteCompMsg;
    }

    public void setDeleteCompMsg(String deleteCompMsg) {
        this.deleteCompMsg = deleteCompMsg;
    }

    public String getDeleteAppMsg() {
        return deleteAppMsg;
    }

    public void setDeleteAppMsg(String deleteAppMsg) {
        this.deleteAppMsg = deleteAppMsg;
    }
    //Other getters/setters

}

    /pages/home.xhtml @424,149 
value="#{homeBean.selectedApplication.licenseRequired}": 
Target Unreachable, 'selectedApplication' returned null