Question

有没有办法让JSF与通用实体一起工作，如下所述：

Property.java

    public interface MyProperty<T> {
        void setMyValue(T value);
        T getMyValue(T value);
    }

在我的申请T中Date，String，Integer或Long只能

MyObject.java

    public class MyObject {
        List<MyProperty<?>> properties;

        public List<MyProperty<?>> getProperties() {
            return properties;
        }
    }

MyController.java

@Named("controller")
@RequestScoped
public class MyController {

    MyObject myObject;
    public void setMyObject(MyObject myObject) { this.myObject = myObject; };
    public MyObject getMyObject() { return myObject; } ;
}

edit.xhtml

<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:ui="http://java.sun.com/jsf/facelets"
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:f="http://java.sun.com/jsf/core">

    <h:head><title></title></h:head><h:body>
    <h:form>
    <ui:repeat  var="property" value="#{controller.myObject.properties}">
        <h:inputText value="#{property.myValue}"/>
    </ui:repeat>
        <h:commandButton action="#{controller.save}" value="save"/>
    </h:form>
    </h:body>
</html>

不幸的是，这不起作用，因为JSF尝试使用签名在myObject上找到一个setter：

void setMyValue(String value);

这显然不存在，因为类型擦除导致该方法具有以下签名：

void setMyValue(Object value);

有没有办法绕过这个？

Answer 1

您的回答不清楚，但答案肯定是是，JSF可以附带仿制药。

但是，这取决于你使用泛型的明智的方式，最终取决于你是否真的理解泛型。

据我所知，您将使用通用接口作为包装器到实现类中包含的对象。

使用带有包装的getter / setters

的类

使用这种方法，您不直接处理MyInterface实现，而是直接处理接口方法定义的内容。

基础界面：

public interface MyInterface<T> {
    void setMyValue(T value);
    T getMyValue();
}

实施班级：

public class MyString implements MyInterface<String> {

    private String myValue;

    public MyString(String myValue) {
        this.myValue = myValue;
    }

    public void setMyValue(String value) {
        this.myValue = value;
    }

    public String getMyValue() {
        return myValue;
    }

    @Override
    public String toString() {
        return myValue;
    }

}

和

public class MyInteger implements MyInterface<Integer> {

    private Integer myValue;

    public MyInteger(Integer myValue) {
        this.myValue = myValue;
    }

    public void setMyValue(Integer value) {
        this.myValue = value;
    }

    public Integer getMyValue() {
        return myValue;
    }

    @Override
    public String toString() {
        return Integer.toString(myValue);
    }

}

托管bean（使用匿名类）：

@ManagedBean
@RequestScoped
public class MyInterfaceBean {

    private MyString myString;
    private MyInteger myInteger;
    private MyInterface<Float> myFloat;

    public MyInterfaceBean() {
        myString = new MyString("String");
        myInteger = new MyInteger(1);
        myFloat = new MyInterface<Float>() {

            private Float myValue;

            public void setMyValue(Float value) {
                this.myValue = value;
            }

            public Float getMyValue() {
                return myValue;
            }

            @Override
            public String toString() {
                return Float.toString(myValue);
            }

        };
        myFloat.setMyValue(3.1f);
    }

    public String getMyString() {
        return myString.getMyValue();
    }

    public void setMyString(String myString) {
        this.myString.setMyValue(myString);
    }

    public Integer getMyInteger() {
        return myInteger.getMyValue();
    }

    public void setMyInteger(Integer myInteger) {
        this.myInteger.setMyValue(myInteger);
    }

    public Float getMyFloat() {
        return myFloat.getMyValue();
    }

    public void setMyFloat(Float myFloat) {
        this.myFloat.setMyValue(myFloat);
    }

    public String action() {
        return null;
    }

}

观点：

<h:outputText value="String: #{myInterfaceBean.myString}"/>
<br/>
<h:outputText value="Integer: #{myInterfaceBean.myInteger}"/>
<br/>
<h:outputText value="Float: #{myInterfaceBean.myFloat}"/>
<br/>
<h:form>
    <h:outputText value="String: "/><h:inputText value="#{myInterfaceBean.myString}"/>
    <br/>
    <h:outputText value="Integer: "/><h:inputText value="#{myInterfaceBean.myInteger}"/>
    <br/>
    <h:outputText value="Float: "/><h:inputText value="#{myInterfaceBean.myFloat}"/>
    <br/>
    <h:commandButton value="Submit" action="#{myInterfaceBean.action}"/>
</h:form>

使用 @FacesConverter

的类

另一种方法是使用@FacesConverter，以便JSF知道如何将输入字段中的字符串转换为实现MyInterface的对象。

托管bean（使用匿名类）：

@ManagedBean
@RequestScoped
public class MyInterfaceBean {

    private MyString myString;
    private MyInteger myInteger;
    private MyInterface<Float> myFloat;

    public MyInterfaceBean() {
        myString = new MyString("String");
        myInteger = new MyInteger(1);
        myFloat = new MyInterface<Float>() {

            private Float myValue;

            public void setMyValue(Float value) {
                this.myValue = value;
            }

            public Float getMyValue() {
                return myValue;
            }

            @Override
            public String toString() {
                return Float.toString(myValue);
            }

        };
        myFloat.setMyValue(3.1f);
    }

    public MyString getMyString() {
        return myString;
    }

    public void setMyString(MyString myString) {
        this.myString = myString;
    }

    public MyInteger getMyInteger() {
        return myInteger;
    }

    public void setMyInteger(MyInteger myInteger) {
        this.myInteger = myInteger;
    }

    public MyInterface<Float> getMyFloat() {
        return myFloat;
    }

    public void setMyFloat(MyInterface<Float> myFloat) {
        this.myFloat.setMyValue(myFloat.getMyValue());//not to lose this anonymous class, can substitute for other implementation directly
    }

    public String action() {
        return null;
    }

}

转换器：

@FacesConverter(value = "myStringConverter")
public class MyStringConverter implements Converter {

    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        if(value == null || value.equals("")) {
            return null;
        }
        MyString obj = new MyString(value);
        return obj;
    }

    public String getAsString(FacesContext context, UIComponent component, Object value) {
        if (!(value instanceof MyString) || (value == null)) {
            return null;
        }
        return ((MyString)value).getMyValue();
    }

}

和

@FacesConverter(value = "myIntegerConverter")
public class MyIntegerConverter implements Converter {

    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        if(value == null || value.equals("")) {
            return null;
        }
        MyInteger obj = null;
        try {
            Integer integer = Integer.valueOf(value);
            obj = new MyInteger(integer);
        } catch(NumberFormatException nfe) {
            throw new ConverterException(new FacesMessage("Integer could not be parsed from string: " + value));
        }
        return obj;
    }

    public String getAsString(FacesContext context, UIComponent component, Object value) {
        if (!(value instanceof MyInteger) || (value == null)) {
            return null;
        }
        return ((MyInteger)value).getMyValue().toString();
    }

}

和

@FacesConverter(value = "myFloatConverter")
public class MyFloatConverter implements Converter {

    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        if(value == null || value.equals("")) {
            return null;
        }
        MyInterface<Float> obj = null;
        try {
            Float floatValue = Float.valueOf(value);
            obj = new MyInterface<Float>() {

                private Float myValue;

                public void setMyValue(Float value) {
                    this.myValue = value;
                }

                public Float getMyValue() {
                    return myValue;
                }

                @Override
                public String toString() {
                    return Float.toString(myValue);
                }

            };
            obj.setMyValue(floatValue);
        } catch(NumberFormatException nfe) {
            throw new ConverterException(new FacesMessage("Float could not be parsed from string: " + value));
        }
        return obj;
    }

    public String getAsString(FacesContext context, UIComponent component, Object value) {
        if (!(value instanceof MyInterface) || (value == null)) {
            if(!(((MyInterface)value).getMyValue() instanceof Float)) {
                return null;
            }
        }
        return ((MyInterface)value).getMyValue().toString();
    }

}

观点：

<h:outputText value="String: #{myInterfaceBean.myString}"/>
<br/>
<h:outputText value="Integer: #{myInterfaceBean.myInteger}"/>
<br/>
<h:outputText value="Float: #{myInterfaceBean.myFloat}"/>
<br/>
<h:form>
    <h:outputText value="String: "/><h:inputText value="#{myInterfaceBean.myString}" converter="myStringConverter"/>
    <br/>
    <h:outputText value="Integer: "/><h:inputText value="#{myInterfaceBean.myInteger}" converter="myIntegerConverter"/>
    <br/>
    <h:outputText value="Float: "/><h:inputText value="#{myInterfaceBean.myFloat}" converter="myFloatConverter"/>
    <br/>
    <h:commandButton value="Submit" action="#{myInterfaceBean.action}"/>
</h:form>

有没有办法让JSF与Generic setter和getter一起使用

1 个答案:

使用带有包装的getter / setters

使用 @FacesConverter