如何为xml实现简单的un/marshalling ?

Question

我试图用Java为我的xml文件创建一个简单的un/marshalling。我在网上找到了一些很好的例子，并试着照着做，但这对我不起作用。这里有两个链接，它们实现的东西与我想要的非常相似:http://www.mkyong.com/java/jaxb-hello-world-example/和使用jaxb (unmarshal)将XML转换为Java对象

当我运行我的代码，我得到这个:

Exception in thread "main" com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 6 counts of IllegalAnnotationExceptions
Property value1 is present but not specified in @XmlType.propOrder
this problem is related to the following location:
    at public java.lang.String Location.getValue1()
    at Location
    at public java.util.List Locations.getLocation()
    at Locations
Property value2 is present but not specified in @XmlType.propOrder
this problem is related to the following location:
    at public int Location.getValue2()
    at Location
    at public java.util.List Locations.getLocation()
    at Locations
Property value3 is present but not specified in @XmlType.propOrder
this problem is related to the following location:
    at public java.lang.String Location.getValue3()
    at Location
    at public java.util.List Locations.getLocation()
    at Locations
Property Value1 appears in @XmlType.propOrder, but no such property exists. Maybe you meant value1?
this problem is related to the following location:
    at Location
    at public java.util.List Locations.getLocation()
    at Locations
Property Value2 appears in @XmlType.propOrder, but no such property exists. Maybe you meant value2?
this problem is related to the following location:
    at Location
    at public java.util.List Locations.getLocation()
    at Locations
Property Value3 appears in @XmlType.propOrder, but no such property exists. Maybe you meant value3?
this problem is related to the following location:
    at Location
    at public java.util.List Locations.getLocation()
    at Locations
at com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException$Builder.check(IllegalAnnotationsException.java:91)
at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getTypeInfoSet(JAXBContextImpl.java:445)
at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:277)
at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:124)
at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1123)
at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:147)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:247)
at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:234)
at javax.xml.bind.ContextFinder.find(ContextFinder.java:462)
at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:641)
at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:584)
at main.main(main.java:18)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)

我的xml是这样的:

<?xml version="1.0" encoding="utf-8" ?>
<Locations>
    <Location>
        <Value1>one</Value1>
        <Value2>1</Value2>
        <Value3>a</Value3>
    </Location>
    <Location>
        <Value1>two</Value1>
        <Value2>2</Value2>
        <Value3>b</Value3>
    </Location>
    <Location>
        <Value1>three</Value1>
        <Value2>3</Value2>
        <Value3>c</Value3>
    </Location>
</Locations>

下面是我的两个对象类:

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import java.util.List;

@XmlRootElement
public class Locations {
    List<Location> location;
    @XmlElement(name="Location")
    public List<Location> getLocation() {
        return location;
    }
    public void setLocation(List<Location> myLocation) {
        this.location = myLocation;
    }
}

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlType;
@XmlType(propOrder = {"Value1", "Value2", "Value3"})
public class Location {
    String Value1;
    int Value2;
    String Value3;
    public String getValue1() {
        return Value1;
    }
    @XmlElement
    public void setValue1(String Value1) {
        this.Value1 = Value1;
    }
    public int getValue2() {
        return Value2;
    }
    @XmlElement
    public void setValue2(int Value2) {
        this.Value2 = Value2;
    }
    public String getValue3() {
        return Value3;
    }
    @XmlElement
    public void setValue3(String Value3) {
        this.Value3 = Value3;
    }
}

这是我的main:

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.*;
import java.io.File;
public class main {
    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Locations.class);
        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("C:\files\Settings.xml");
        Locations locations = (Locations) unmarshaller.unmarshal(xml);
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(locations, System.out);
    }
}

Answer 1

基本上，这里有一个大小写问题—在XML文件中，标记都以大写字母开头。在java类中，您用@XmlElement注释了setter，从而指示JAXB使用这些setter进行编组/解组。然而，根据JavaBeans规范第8.3节，setter方法setValue1暗示属性命名为value1(小写!)。

因此必须显式地告诉JAXB要映射到Java类的属性的XML中的属性的正确名称(区分大小写!)。例如，在您的例子中，您必须告诉Value1必须映射到Java属性value1。您可以通过用@XmlElement(name="Value1")注释setter方法来实现这一点。propOrder的值必须与Java类的属性相关，而不是与XML标记相关。

下面的方法对我有用:

   public static void main(String[] args) throws JAXBException {
        JAXBContext jc = JAXBContext.newInstance(Locations.class, Location.class);
        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("D:\temp\Settings.xml");
        Locations locations = (Locations) unmarshaller.unmarshal(xml);
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(locations, System.out);
    }
    @XmlRootElement(name = "Locations")
    private static class Locations {
        List<Location> location;
        public List<Location> getLocation() {
            return location;
        }
        @XmlElement(name = "Location")
        public void setLocation(List<Location> myLocation) {
            this.location = myLocation;
        }
    }
    @XmlType(propOrder = { "value1", "value2", "value3" })
    private static class Location {
        String Value1;
        int Value2;
        String Value3;
        public String getValue1() {
            return Value1;
        }
        @XmlElement(name = "Value1")
        public void setValue1(String Value1) {
            this.Value1 = Value1;
        }
        public int getValue2() {
            return Value2;
        }
        @XmlElement(name = "Value2")
        public void setValue2(int Value2) {
            this.Value2 = Value2;
        }
        public String getValue3() {
            return Value3;
        }
        @XmlElement(name = "Value3")
        public void setValue3(String Value3) {
            this.Value3 = Value3;
        }
    }

Answer 2

在类位置使用

@XmlType(propOrder = {"value1", "value2", "value3"})

和class Locations

@XmlRootElement(name = "Locations")

我还建议遵守Java命名约定，即变量首字母小写(类名大写)。例如Value1到Value1, Value2到Value2, Value3到Value3