属性未从视图发送到控制器

从您的stacktrace消息中：

java.lang.NullPointerException: null    at org.springframework.samples.knowledgemanager.model.CPTCode.getId(CPTCode.java:30) ~[CPTCode.class:na]

这表示的

id

CPTCode

NullPointerException

因此，要使用您的代码，请更改以下内容：

要在表单中添加带有CPTCode的选择框，请进行如下修改：

 <form:form modelAttribute="encounter" method="post"  action="${actUrl}">    <div >        <form:select path="preSelected" items="${encounterpres}" size="5" />    </div>    <form:hidden path="id"/>    <td>    </td>    <div >        <button type="submit">Add a Billing Code</button> <h3>    link to delete will go here.</h3>    </div></form:form>

然后，使用getter和setter 将变量添加

private Integer preSelected;

Encounter

在您的控制器中填充遭遇代码，例如：

@ModelAttribute("encounterpres") public Map populateEncounterpres() {    Map<Integer, String> encCodes = new linkedHashMap<Integer, String>();    for(CPTCode cpt: this.clinicService.findEncounterpres()){      encCodes.put(cpt.getId(), cpt.getName());    }    return encCodes; }

并在您的POST中进行如下修改：

    @RequestMapping(value = "/patients/{patientId}/encounters/{encounterId}/pres", method = {RequestMethod.POST})     public String processUpdateCodesForm(@ModelAttribute("encounter") Encounter encounter, @PathVariable("encounterId") int eid, BindingResult result, SessionStatus status) {        Encounter myencounter = this.clinicService.findEncounterById(eid);        CPTCode myCode = this.clinicService.findCPTCodeById(encounter.getCodeSelected());        myencounter.addCode(myCode);        return "redirect:/encounters?encounterID={encounterId}";     }