如何解决此异常，无法将java.lang.String强制转换为用户定义的类型 [英] How to fix this exception java.lang.String cannot be cast to user defined type

问题描述

伙计们，我正在尝试遍历用户定义对象的列表，但是却收到此错误(java.lang.String无法转换为bg.fmi.master.thesis.model.TFilterType)，我无法弄清楚为什么.

guys, i am trying to iterate though a list of user defined objects but i get this error (java.lang.String cannot be cast to bg.fmi.master.thesis.model.TFilterType) and i can not figure out why.

我的.xhtml我有:

I my .xhtml i have:

<p:selectManyCheckbox id="chkbox1"
                    value="#{requestBean.selectedBooleanFilterTypes}"
                    layout="pageDirection">
                    <f:selectItems var="checkbox"
                        value="#{filterTypeBean.listBooleanFilterTypes()}"
                        itemLabel="#{checkbox.filterTypeName}" itemValue="#{checkbox}" />
                    <!-- required="true"
                         requiredMessage="check at least one checkbox"  -->

                </p:selectManyCheckbox>

来自bean类的部分:

Part from the bean class:

private List<TFilterType> selectedBooleanFilterTypes;

public List<TFilterType> getSelectedBooleanFilterTypes() {
        return selectedBooleanFilterTypes;
    }

    public void setSelectedBooleanFilterTypes(
            List<TFilterType> selectedBooleanFilterTypes) {
        this.selectedBooleanFilterTypes = selectedBooleanFilterTypes;
    }

这是另一种方法的一部分，但在bean类中也是如此:

This is part from another method, but also in the bean class:

for (TFilterType type : selectedBooleanFilterTypes) {
            System.out.println("SelectedFilterTypes: "
                    + type.getFilterTypeName());
        }

在调试模式下，我可以看到selectedBooleanFilterTypes具有以下值:

During Debugging mode i can see that selectedBooleanFilterTypes has this value:

[TFilterType [filterTypeName = DJ，filterTypeDesc = DJ，isBooleanType = B，tRequestFilters = []]，TFilterType [filterTypeName =Украса，filterTypeDesc = Decoration，isBooleanType = B，tRequestFilters = []]

[TFilterType [filterTypeName=DJ, filterTypeDesc=DJ, isBooleanType=B, tRequestFilters=[]], TFilterType [filterTypeName=Украса, filterTypeDesc=Decoration, isBooleanType=B, tRequestFilters=[]]]

提前谢谢！

推荐答案

TFilterType是Java类.在这种情况下，您应该使用Faces Converter作为您的类型.
请尝试以下示例

TFilterType is a Java class. in this case you should use a faces converter for your type.
please try this sample

xhtml:

<p:selectManyCheckbox id="chkbox1" value="#{requestBean.selectedBooleanFilterTypes}"
                      layout="pageDirection" converter="filterTypeConverter">
    <f:selectItems var="checkbox" value="#{filterTypeBean.listBooleanFilterTypes()}"
                   itemLabel="#{checkbox.filterTypeName}" itemValue="#{checkbox}"/>
</p:selectManyCheckbox>

转换器:

@FacesConverter("filterTypeConverter")
public class TFilterTypeConverter implements Converter {

    @Override
    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        FilterTypeBean filterTypeBean = context.getApplication().evaluateExpressionGet(context, "#{filterTypeBean}", FilterTypeBean.class);
        for (TFilterType type : filterTypeBean.listBooleanFilterTypes()) {
            if (type.getFilterTypeName().equals(value)) {
                return type;
            }
        }
        return null;
    }

    @Override
    public String getAsString(FacesContext context, UIComponent component, Object value) {
        if (value instanceof TFilterType) {
            return ((TFilterType) value).getFilterTypeName();
        } else {
            return "";
        }
    }
}

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