Question

假设我有一个月，日和年选择。每一个选择一个。现在我需要将它们绑定到一个支持bean属性 - java.util.Date。我如何实现目标？

Answer 1

三种方式：

以java.util.Calendar为后退或中间，有三个吸气剂和三个吸气剂。
使用Converter，但这有点像hacky。
使用rich:calendar等第三方组件。

编辑，以下是选项2的外观。

page.jsp：

<h:form>
    <h:selectOneMenu value="#{myBean.date}">
        <f:converter converterId="datePartConverter" />
        <f:attribute name="part" value="day" />
        <f:selectItems value="#{myBean.days}" />
    </h:selectOneMenu>
    <h:selectOneMenu value="#{myBean.date}">
        <f:converter converterId="datePartConverter" />
        <f:attribute name="part" value="month" />
        <f:selectItems value="#{myBean.months}" />
    </h:selectOneMenu>
    <h:selectOneMenu value="#{myBean.date}">
        <f:converter converterId="datePartConverter" />
        <f:attribute name="part" value="year" />
        <f:selectItems value="#{myBean.years}" />
    </h:selectOneMenu>

    <h:commandButton value="submit" action="#{myBean.submit}"/>
    <h:messages />
</h:form>

mypackage.MyBean：

package mypackage;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import javax.faces.model.SelectItem;

public class MyBean {

    private static List<SelectItem> days = new ArrayList<SelectItem>();
    private static List<SelectItem> months = new ArrayList<SelectItem>();
    private static List<SelectItem> years = new ArrayList<SelectItem>();

    static {
        // Just do your thing to fill them. Only ensure that those are Strings,
        // else you'll need to change the type in Converter accordingly.
        for (int i = 1; i <= 31; i++) days.add(new SelectItem(String.valueOf(i)));
        for (int i = 1; i <= 12; i++) months.add(new SelectItem(String.valueOf(i)));
        for (int i = 2000; i <= 2020; i++) years.add(new SelectItem(String.valueOf(i)));
    }

    private Date date;

    public void submit() {
        // Print submitted date to stdout.
        System.out.println("Submitted date: " + date);
    }

    public List<SelectItem> getDays() {
        return days;
    }

    public List<SelectItem> getMonths() {
        return months;
    }

    public List<SelectItem> getYears() {
        return years;
    }

    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

}

mypackage.DatePartConverter：

package mypackage;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Map;

import javax.faces.application.FacesMessage;
import javax.faces.component.UIComponent;
import javax.faces.component.UIInput;
import javax.faces.context.FacesContext;
import javax.faces.convert.Converter;
import javax.faces.convert.ConverterException;

public class DatePartConverter implements Converter {

    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        String part = (String) component.getAttributes().get("part");
        Date date = null;

        if (context.getRenderResponse()) {
            // Convert any default/selected date for display.
            Date selectedDate = (Date) ((UIInput) component).getValue();
            if (selectedDate != null) {
                if (("day".equals(part) && new SimpleDateFormat("d").format(selectedDate).equals(value))
                    || ("month".equals(part) && new SimpleDateFormat("M").format(selectedDate).equals(value))
                    || ("year".equals(part) && new SimpleDateFormat("yyyy").format(selectedDate).equals(value)))
                {
                    date = selectedDate;
                }
            }
        } else {
            // Convert submitted date after submit.
            Map<String, Object> map = context.getExternalContext().getRequestMap();
            if ("day".equals(part)) {
                map.put("DatePartConverter.day", value); // Save until we have all parts.
            } else if ("month".equals(part)) {
                map.put("DatePartConverter.month", value); // Save until we have all parts.
            } else if ("year".equals(part)) {
                String day = (String) map.get("DatePartConverter.day");
                String month = (String) map.get("DatePartConverter.month");
                String dateString = String.format("%s-%s-%s", day, month, value);

                try {
                    date = new SimpleDateFormat("d-M-yyyy").parse(dateString);
                } catch (ParseException e) {
                    throw new ConverterException(new FacesMessage(e.getMessage()), e);
                }
            }
        }

        return date;
    }

}

    public String getAsString(FacesContext context, UIComponent component, Object value) {
        // Not relevant here. Just return SelectItem's value.
        return (String) value;
    }

faces-config.xml

<converter>
    <converter-id>datePartConverter</converter-id>
    <converter-class>mypackage.DatePartConverter</converter-class>
</converter>

<managed-bean>
    <managed-bean-name>myBean</managed-bean-name>
    <managed-bean-class>mypackage.MyBean</managed-bean-class>
    <managed-bean-scope>request</managed-bean-scope>
</managed-bean>

请注意，没有Validator，SimpleDateFormat默认为lenient。因此，选择例如11月31日将产生12月1日。如果您想要警告，可能需要自己实施DatePartValidator。

Answer 2

当说“绑定”和“支持bean”时，你应该参考以下内容：

<h:inputText binding="#{myBean.myTextField}" />

并在您的bean中有private UIInput。

如果是这种情况 - 不，你不能这样绑定。好吧，我不确定你在技术上是否可以 - 但肯定会有意想不到的效果。

但是，如果您想要定位托管bean属性，那么您可以，例如：

<h:inputText value="#{myBean.myProperty.day}" />
<h:inputText value="#{myBean.myProperty.year}" />

使用Java Server Faces将多个输入字段绑定到backing bean属性？

2 个答案: