在wicket 8.x版本中，指示按钮单击时出现以下错误。
错误|发生异常：java.lang.illegalstateexception:尝试在没有模型的组件上设置模型对象！将imodel传递给构造函数或使用#setdefaultmodel（newsomemodel（object））。组成部分：form:savedquery at org.apache.wicket.component.setdefaultmodelobject（组件。java:2999)位于org.apache.wicket.igenericcomponent.setmodelobject（igenericcomponent。java:81)在org.apache.wicket.markup.html.form.formcomponent.updatemodel（formcomponent。java:1100)在org.apache.wicket.markup.html.form.form$formmodelupdatevisitor.component（表单。java:223)在org.apache.wicket.markup.html.form.form$formmodelupdatevisitor.component（form。java:193)访问org.apache.wicket.util.visit.visits.visitpostorderhelper（visits。java:274)访问org.apache.wicket.util.visit.visits.visitpostorderhelper（visits。java:262)在org.apache.wicket.util.visit.visits.visitpostorder（访问。java:245)在org.apache.wicket.markup.html.form.formcomponent.visitComponentsStorder（formcomponent。java:426)位于org.apache.wicket.markup.html.form.form.internalupdateformcomponentmodels（表单。java:1873)在org.apache.wicket.markup.html.form.form.updateformcomponentmodels（表单。java:1838)在org.apache.wicket.markup.html.form.form.process（表单。java:990)在org.apache.wicket.markup.html.form.form.onformsubmitted（form。java:825)在org.apache.wicket.ajax.form.ajaxformsubmitbehavior.onevent（ajaxformsubmitbehavior。java:176)在org.apache.wicket.ajax.ajaxeventbehavior.respond（ajaxeventbehavior。java:127)在org.apache.wicket.ajax.abstractdefaultajaxbehavior.onrequest（abstractdefaultajaxbehavior）。java:598)在org.apache.wicket.core.request.handler.listenerrequesthandler.internalinvoke（listenerrequesthandler。java:306)在org.apache.wicket.core.request.handler.listenerrequesthandler.invoke（listenerrequesthandler。java:280)在org.apache.wicket.core.request.handler.listenerrequesthandler.invokelistener（listenerrequesthandler。java:222)在org.apache.wicket.core.request.handler.listenerrequesthandler.respond（listenerrequesthandler。java:208)在org.apache.wicket.request.cycle.requestcycle$handlerexecutor.respond（requestcycle。java:914)在org.apache.wicket.request.requesthandlerexecutor.execute（requesthandlerexecutor。java:65)在org.apache.wicket.request.cycle.requestcycle.execute（requestcycle。java:282)在org.apache.wicket.request.cycle.requestcycle.processrequest（requestcycle。java:253)在org.apache.wicket.request.cycle.requestcycle.processrequestanddetach（requestcycle。java:221) 在org.apache.wicket.protocol.http.wicketfilter.processrequestcycle（wicketfilter。java:275)在org.apache.wicket.protocol.http.wicketfilter.processrequest（wicketfilter。java:206)在org.apache.wicket.protocol.http.wicketfilter.dofilter（wicketfilter。java:299)在org.apache.catalina.core.applicationfilterchain.internaldofilter（applicationfilterchain）。java:193)在org.apache.catalina.core.applicationfilterchain.dofilter（applicationfilterchain。java:166)在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:320)在org.springframework.security.web.access.intercept.filtersecurityinterceptor.invoke（filtersecurityinterceptor。java:126)在org.springframework.security.web.access.intercept.filtersecurityinterceptor.dofilter（filtersecurityinterceptor。java:90)在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:334) 在org.springframework.security.web.access.exceptiontranslationfilter.dofilter（exceptiontranslationfilter。java:118)在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:334)在org.springframework.security.web.session.sessionmanagementfilter.dofilter（sessionmanagementfilter。java:137)在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:334)在org.springframework.security.web.authentication.anonymousauthenticationfilter.dofilter（anonymousauthenticationfilter。java:111)在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:334)在org.springframework.security.web.authentication.rememberme.rememberAuthenticationFilter.dofilter（rememberAuthenticationFilter）。java:158)在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:334)在org.springframework.security.web.servletapi.securitycontextholderawarerequestfilter.dofilter（securitycontextholderawarerequestfilter）。java:158)在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:334)在org.springframework.security.web.savedrequest.requestcacheawarefilter.dofilter（requestcacheawarefilter。java:63)在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:334)在org.springframework.security.web.authentication.验证。www.basicauthenticationfilter.dofilterinternal（基本身份验证筛选器。java:204)在org.springframework.web.filter.onceperrequestfilter.dofilter（onceperrequestfilter。java:119)在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:334)在org.springframework.security.web.header.headerwriterfilter.doheadersafter（headerwriterfilter。java:92)在org.springframework.security.web.header.headerwriterfilter.dofilterinternal（headerwriterfilter。java:77)在org.springframework.web.filter.onceperrequestfilter.dofilter（onceperrequestfilter。java:119)在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:334)位于org.springframework.security.web.context.request.async.webasyncmanagerintegrationfilter.dofilterinternal（webasyncmanagerintegrationfilter）。java:56)在org.springframework.web.filter.onceperrequestfilter.dofilter（onceperrequestfilter。java:119) 在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:334)位于org.springframework.security.web.context.securitycontextpersistencefilter.dofilter（securitycontextpersistencefilter）。java:105)在org.springframework.security.web.filterchainproxy$virtualfilterchain.dofilter（filterchainproxy。java:334)在org.springframework.security.web.filterchainproxy.dofilternternal（filterchainproxy。java:215)在org.springframework.security.web.filterchainproxy.dofilter（filterchainproxy。java:178)在org.springframework.web.filter.delegatingfilterproxy.invokedelegate（delegatingfilterproxy。java:358)在org.springframework.web.filter.delegatingfilterproxy.dofilter（delegatingfilterproxy。java:271)位于org.apache.catalina.core.applicationfilterchain.internaldofilter（applicationfilterchain）。java:193)在org.apache.catalina.core.applicationfilterchain.dofilter（applicationfilterchain。java:166)在org.apache.catalina.core.standardwrappervalve.invoke（standardwrappervalve。java:199)在org.apache.catalina.core.standardcontextvalve.invoke（standardcontextvalve。java:96)在org.apache.catalina.authenticator.authenticatorbase.invoke（authenticatorbase。java:543)在org.apache.catalina.core.standardhostvalve.invoke（standardhostvalve。java:139)在org.apache.catalina.valves.errorreportvalve.invoke（errorreportvalve。java:81)在org.apache.catalina.valves.abstractaccesslogvalve.invoke（abstractaccesslogvalve。java:688)在org.apache.catalina.core.standardenginevalve.invoke（standardenginevalve。java:87)在org.apache.catalina.connector.coyoteadapter.service（coyoteadapter。java:343)在org.apache.coyote.http11.http11processor.service（http11processor。java:615)在org.apache.coyote.abstractprocessorlight.process（abstractprocessorlight。java:65)在org.apache.coyote.abstractprotocol$connectionhandler.process（abstractprotocol。java:818)位于org.apache.tomcat.util.net.nioendpoint$socketprocessor.dorun（nioendpoint）。java:1623)在org.apache.tomcat.util.net.socketprocessorbase.run（socketprocessorbase。java:49)位于java.util.concurrent.threadpoolexecutor.runworker（threadpoolexecutor。java:1149)在java.util.concurrent.threadpoolexecutor$worker.run（threadpoolexecutor。java:624)在org.apache.tomcat.util.threads.taskthread$wrappingrunnable.run（taskthread。java:61)在java.lang.thread.run（线程。java:748)

final DropDownChoice<String> listSites = (DropDownChoice<String>) new DropDownChoice<String>("savedQueries", new PropertyModel<String>(TestPage.this.getModel(), "selectedValue"), savedQueries).add(new FormComponentUpdatingBehavior() {
private static final long serialVersionUID = 1L;

protected void onUpdate() {
    // Update logic
}

    protected void onError(RuntimeException ex) {
        super.onError(ex);
    }
});

listSites.setOutputMarkupId(true);
add(listSites); 

TextField savedQuery = new TextField<>("savedQuery"); // CHECK LATER 
savedQuery.setOutputMarkupId(true);
add(savedQuery);

final IndicatingAjaxButton deleteMcb = new IndicatingAjaxButton("delete") {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    @Override
    protected void onSubmit(AjaxRequestTarget target) {
        String message=null;
        List<String> savedQueries = null;
        try{
            //on submit process logic
        }catch(Exception e){
            e.printStackTrace();
        }

        listSites.setChoices(savedQueries);
        listSites.setModelObject(null);
        target.add(listSites);
        savedQuery.setModelObject(null);
        target.add(savedQuery);
        target.add(feedback);
        error(message);
    }

};