Primefaces selectOneListbox value is null

Question

我需要一些帮助来解决一些我不理解的事情:

所以我想删除一个项目从一个selectOneListBox使用命令按钮，但问题是，当我按下这个按钮，它使用setter方法，但值总是空…我要显示代码

farm.xhtml

<h:form>
    <h:panelGrid columns="1" columnClasses="label, value"
        cellpadding="10">
        <h:panelGroup style="width: 90%">
            <p:inputText id="cropVariation" style="margin-right: 10px"
                label="#{msg['farms.form.farmBasicInformation.cropVariation']}"
                value="#{farmsController.cropVariation}" />
            <p:inputText id="cropRotation" style="margin-right: 10px"
                label="#{msg['farms.form.farmBasicInformation.cropRotation']}"
                value="#{farmsController.cropRotation}" />
            <p:watermark for="cropVariation"
                value="#{msg['farms.form.farmBasicInformation.cropVariation']}" />
            <p:watermark for="cropRotation"
                value="#{msg['farms.form.farmBasicInformation.cropRotation']}" />
            <p:commandButton value="#{msg['buttons.add']}"
                action="#{farmsController.addCrop()}" ajax="true"
                icon="ui-icon-plus"
                update="majorCropsSelect cropRotation cropVariation"
                process="cropVariation cropRotation @this" />
        </h:panelGroup>
    </h:panelGrid>
    <p:fragment autoUpdate="true">
        <h:panelGrid columns="2" columnClasses="label, value">
            <p:selectOneListbox id="majorCropsSelect"
                style="width: 450px"
                value="#{farmsController.selectedCrop}"
                converter="#{selectOneListBoxConverter}">
                <f:selectItems value="#{farmsController.majorCrops}"
                    var="majorCrop" itemLabel="#{majorCrop}"
                    itemValue="#{majorCrop}" />
                <p:column>
                    <h:outputText value="#{majorCrop}" />
                </p:column>
            </p:selectOneListbox>
            <p:commandButton value="#{msg['buttons.remove']}"
                action="#{farmsController.removeCrop()}" ajax="true"
                icon="ui-icon-minus"/>
        </h:panelGrid>
    </p:fragment>
</h:form>

FarmsController.java

@ManagedBean
@Controller
@ViewScoped
public class FarmsController extends BaseController {
    @Autowired
    private FarmsService farmsService;
    @Autowired
    private SecurityService securityService;
    public static String BEAN_PAGE = "farm.jsf";
    public static String LIST_PAGE = "farmsManagement.jsf";
    private Farm currentFarm;
    private List<MajorCrop> majorCrops = new ArrayList<MajorCrop>();
    private MajorCrop selectedCrop = null;
    private String cropVariation;
    private String cropRotation;
public void removeCrop() {
        if (selectedCrop != null) {
            majorCrops.remove(selectedCrop);
        }
    }
public MajorCrop getSelectedCrop() {
        return selectedCrop;
    }
    public void setSelectedCrop(MajorCrop selectedCrop) {
        this.selectedCrop = selectedCrop; (here the value 'selectedCrop' is always null)
    }
public List<MajorCrop> getMajorCrops() {
        return majorCrops;
    }
    public void setMajorCrops(List<MajorCrop> majorCrops) {
        this.majorCrops = majorCrops;
    }
}

SelectOneListBoxConverter.java

@Component("selectOneListBoxConverter")
@FacesConverter(forClass=FarmsController.class, value="selectOneListBoxConverter")
public class SelectOneListBoxConverter implements Converter {
    @Override
    public Object getAsObject(FacesContext context, UIComponent component,
            String value) {
        SelectOneListbox p = (SelectOneListbox) component;
        MajorCrop dl = (MajorCrop) p.getValue();
        return dl;
    }
    @Override
    public String getAsString(FacesContext context, UIComponent component,
            Object value) {
        return value.toString();
    }
}

你知道为什么我可以得到selectedCrop值总是为空吗?

非常感谢!

Answer 1

其实我已经找到问题了。

关键是，在转换器中，我不能使用getValue()属性，因为之前没有设置任何值，所以没有值。

我必须使用value String变量并处理它以获得我想要的对象。下面是代码:

    @Component("selectOneListBoxConverter")
@FacesConverter(forClass = FarmsController.class, value = "selectOneListBoxConverter")
public class SelectOneListBoxConverter implements Converter {
    @Override
    public Object getAsObject(FacesContext context, UIComponent component,
            String value) {
        MajorCrop dl = new MajorCrop();
        String[] values = value.split("\(");
        String name = "";
        for (int i = 0; i < values.length - 1; i++) {
            name += values[i];
        }
        dl.setName(name.substring(0, name.length() - 1));
        dl.setRotations(values[values.length - 1].substring(0,
                values[values.length - 1].length() - 1));
        return dl;
    }
    @Override
    public String getAsString(FacesContext context, UIComponent component,
            Object value) {
        return value.toString();
    }
}