我一直在尝试编写JSF应用程序的成功有限。在应用程序的一个部分中，我需要用户从选择菜单中进行选择，该菜单显示可选状态值列表。 Status类（如下所示），用于填充选择菜单中显示的List，是一个由两个字符串组成的简单类：一个是用于在数据库中查找描述的代码，另一个是人类可读的描述。我试图找出我是否需要转换器，如果是这样，如何最好地实现转换器。这是一个使用Java 1.5的JSF 1.1项目
我在JSP中使用以下代码：
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h"%>
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f"%>
<f:view>
<html>
<h:graphicImage id="image" url="/images/appname.jpg"
alt="app name" />
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<jsp:include page="/jsp/menu.jsp" />
</head>
<body>
<h:outputText
value="Add Value"
style="font-size:20px;" />
<h:messages errorStyle="color: red" infoStyle="color: green"
layout="table" />
<h:form id="statusReasonEditForm">
<table>
<tr>
<td><h:outputText id="txtvalue" value="Status" /></td>
<td><h:selectOneMenu id="selectStatus"
value="#{pc_statusReasonBacker.status}"
binding="#{pc_statusReasonBacker.selectItem}">
<f:selectItems value="#{pc_statusReasonBacker.selectStatuses}" />
<f:converter converterId="statusConverter" />
</h:selectOneMenu>
<td><h:outputText id="txtvaluereason" value="Status Reason" /></td>
<td><h:inputText id="txtinputreason"
value="#{pc_statusReasonBacker.statusReason.statusReason}"
maxlength="100" size="40" /></td>
<td><h:outputText id="txtvaluereasondesc"
value="Status Reason Desc" /></td>
<td><h:inputText id="txtinputreasondesc"
value="#{pc_statusReasonBacker.statusReason.statusReasonDesc}"
maxlength="100" size="40" /></td>
</tr>
</table>
<tr>
<td><h:commandButton id="savebutton" value="Save"
action="#{pc_statusReasonBacker.save}" /></td>
<td><h:commandButton id="cancelbutton" value="Cancel"
action="#{pc_statusReasonBacker.cancel}" /></td>
</tr>
</h:form>
<hr />
</body>
</html>
</f:view>
这里显示了支持bean（为了清楚起见，删除了一些非相关的部分，例如分页）：
公共类StatusReasonBacker {
private List<StatusReason> statusReasonList;
private List<Status> statusList;
private List<SelectItem> selectStatuses;
private StatusReason statusReason;
private StatusDao sDao;
private Status status;
private UIData statusReasonTable;
private HtmlSelectOneMenu selectItem;
private String selectedStatus = "";
public StatusReasonBacker() {
sDao = new StatusDao();
statusReason = new StatusReason();
selectStatuses = new ArrayList<SelectItem>();
status = new Status();
selectItem = new HtmlSelectOneMenu();
}
public String insert() {
status.setStatusCde("");
statusReason.setStatus(status);
statusReason.setStatusReason("");
statusReason.setStatusReasonCde("");
statusReason.setStatusReasonDesc("");
return "success";
}
public String edit() {
this.statusReason = (StatusReason) statusReasonTable.getRowData();
selectItem.setValue(statusReason.getStatus().getStatusCde());
return "success";
}
public String update() {
if ("".equalsIgnoreCase(statusReason.getStatusReason().trim())) {
Message
.addErrorMessage("You must enter a value for the status reason.");
return "failure";
} else if (("".equalsIgnoreCase(statusReason.getStatusReasonDesc()
.trim()))) {
Message
.addErrorMessage("You must enter a value for the status reason description.");
return "failure";
}
sDao.updateStatusReason(statusReason);
return "statusreasons";
}
public String delete() {
StatusReason statReason = (StatusReason) statusReasonTable.getRowData();
sDao.deleteStatusReason(statReason);
return "statusreasons";
}
public String cancel() {
return "statusreasons";
}
public String save() {
statusReason.setStatus(status);
sDao.insertStatusReason(statusReason);
return "statusreasons";
}
...
public StatusDao getSDao() {
return sDao;
}
public void setSDao(StatusDao dao) {
sDao = dao;
}
public List<StatusReason> getStatusReasonList() {
statusReasonList = sDao.getStatusReasons();
return statusReasonList;
}
public void setStatusReasonList(List<StatusReason> statusReasonList) {
this.statusReasonList = statusReasonList;
}
public UIData getStatusReasonTable() {
return statusReasonTable;
}
public void setStatusReasonTable(UIData statusReasonTable) {
this.statusReasonTable = statusReasonTable;
}
public StatusReason getStatusReason() {
return statusReason;
}
public void setStatusReason(StatusReason statusReason) {
this.statusReason = statusReason;
}
public List<Status> getStatusList() {
statusList = sDao.getStatuses();
return statusList;
}
public void setStatusList(List<Status> statusList) {
this.statusList = statusList;
}
public List<SelectItem> getSelectStatuses() {
selectStatuses.clear();
if (statusList == null) {
statusList = this.getStatusList();
}
for (Status sr : statusList) {
SelectItem si = new SelectItem();
si.setValue(sr.getStatusCde());
si.setLabel(sr.toString());
si.setDescription(sr.toString());
selectStatuses.add(si);
}
return selectStatuses;
}
public void setSelectStatuses(List<SelectItem> selectStatuses) {
this.selectStatuses = selectStatuses;
}
public String getSelectedStatus() {
selectedStatus = statusReason.getStatusDesc();
return selectedStatus;
}
public void setSelectedStatus(String selectedStatus) {
this.selectedStatus = selectedStatus;
}
public Status getStatus() {
return status;
}
public void setStatus(Status status) {
this.status = status;
}
public HtmlSelectOneMenu getSelectItem() {
return selectItem;
}
public void setSelectItem(HtmlSelectOneMenu selectItem) {
this.selectItem = selectItem;
}
}
谢谢！
答案 0 :(得分：6)
我试图找出我是否需要转换器，如果是的话，最好如何实现转换器。
只要您希望将非标准Java对象从HTTP请求传递到另一个HTTP请求，就需要转换器。对于非标准，我的意思是不 String，Number或Boolean。这一切都只是因为HTTP请求参数仅为Strings。 Number和Boolean的作用是因为EL可以识别它们并且内置了强制措施。
对于非标准Java对象，您需要实现javax.faces.convert.Converter，将对象转换为String（或Number所需的内容，例如Long id在以HTML格式显示之前，getAsString()方法内的数据库表中关联行的PK可以是PK。在处理请求参数期间，您在getAsObject()方法中执行相反的操作（例如，通过其id从DAO获取关联对象）。
您可以找到here示例，了解如何Converter用于h:selectOneMenu。您看到本文还包含一个替代方案，但您需要在辅助bean中进行更多工作以自行转换（映射）对象。