引起:java.lang.ClassNotFoundException:com.sun.xml.bind.v2.model.annotation.AnnotationReader

Question

您可能认为以下问题非常简单,但我不知道我在这里做错了什么.我觉得我添加了必需的依赖项.不是吗？

有人可以建议我这里有什么不对吗？

Exception in thread "main" java.lang.NoClassDefFoundError: com/sun/xml/bind/v2/model/annotation/AnnotationReader
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
    at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.getDeclaredMethods0(Native Method)
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
    at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
    at java.lang.Class.getMethod0(Class.java:3018)
    at java.lang.Class.getMethod(Class.java:1784)
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:242)
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:234)
    at javax.xml.bind.ContextFinder.find(ContextFinder.java:441)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:641)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:584)
    at com.misc.common.ReadXMLFileJaxb.main(ReadXMLFileJaxb.java:14)
Caused by: java.lang.ClassNotFoundException: com.sun.xml.bind.v2.model.annotation.AnnotationReader
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 23 more

Book.java

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Book {
    @XmlAttribute
    private String firstName;
    @XmlElement
    private String lastName;
    @XmlElement
    private String age;


    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getAge() {
        return age;
    }
    public void setAge(String age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Book [firstName=" + firstName + ", lastName=" + lastName+ ", age=" + age + "]";
    }
}

ReadXMLFileJaxb.java

public class ReadXMLFileJaxb {
    public static void main(String[] args) {
        File file = new File(ReadXMLFileDOM.class.getClassLoader().getResource("book.xml").getFile());

        try {
            JAXBContext context = JAXBContext.newInstance(Book.class);
            Unmarshaller unmarshaller = context.createUnmarshaller();
            Book book = (Book) unmarshaller.unmarshal(file);
            System.out.println(book.toString());
        } catch (JAXBException e) {
            System.out.println(e.getMessage());
        }
    }
}

我的book.xml

<?xml version="1.0"?>
<book>
    <person>
        <first>Kiran</first>
        <last>Pai</last>
        <age>22</age>
    </person>
    <person>
        <first>Bill</first>
        <last>Gates</last>
        <age>46</age>
    </person>
    <person>
        <first>Steve</first>
        <last>Jobs</last>
        <age>40</age>
    </person>
</book>

的pom.xml

<properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <!-- JAXB -->
        <dependency>
            <groupId>com.sun.xml.bind</groupId>
            <artifactId>jaxb-impl</artifactId>
            <version>2.2.11</version>
        </dependency>
        <dependency>
            <groupId>javax.xml.bind</groupId>
            <artifactId>jaxb-api</artifactId>
            <version>2.2.12</version>
        </dependency>
    </dependencies>

Answer 1

根据链接:为什么从JAXB参考实现中删除了AnnotationReader？,你需要简单地使用下面的maven依赖项:

<dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-impl</artifactId>
    <version>2.2.11</version>
</dependency>

<dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-core</artifactId>
    <version>2.2.11</version>
</dependency>

你需要稍微重构一下代码.看起来你还没有创建模型类的相同名称字段,它应该如下所示:Person.java

@XmlRootElement(name="Person")
@XmlAccessorType(XmlAccessType.FIELD)
public class Person {
    @XmlElement
    private String first;
    @XmlElement
    private String last;
    @XmlElement
    private String age;
    public String getFirst() {
        return first;
    }
    public void setFirst(String first) {
        this.first = first;
    }
    public String getLast() {
        return last;
    }
    public void setLast(String last) {
        this.last = last;
    }
    public String getAge() {
        return age;
    }
    public void setAge(String age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Person [first=" + first + ", last=" + last + ", age=" + age + "]";
    }
} 

Book.java

@XmlRootElement(name="book")
@XmlAccessorType(XmlAccessType.FIELD)
public class Book {
    private List<Person> person = new ArrayList<Person>();

    public List<Person> getPerson() {
        return person;
    }

    public void setPerson(List<Person> person) {
        this.person = person;
    }
}

ReadXMLFileJaxb.java

public class ReadXMLFileJaxb {
    public static void main(String[] args) {
        File file = new File(ReadXMLFileDOM.class.getClassLoader().getResource("book.xml").getFile());

        try {
            JAXBContext context = JAXBContext.newInstance(Book.class);
            Unmarshaller unmarshaller = context.createUnmarshaller();
            Book book = (Book) unmarshaller.unmarshal(file);
            System.out.println(book.getPerson().size());

            for (int i = 0; i < book.getPerson().size(); i++) {
                System.out.println("------------");
                System.out.println(book.getPerson().get(i).getFirst());
                System.out.println(book.getPerson().get(i).getLast());
                System.out.println(book.getPerson().get(i).getAge());
            }

        } catch (JAXBException e) {
            System.out.println(e.getMessage());
        }
    }
}

以下输出我看到:

3
------------
Kiran
Pai
22
------------
Bill
Gates
46
------------
Steve
Jobs
40

Answer 2

虽然问题很老但仍在回答.根本原因是com.sun.xml.bind现在已经过时了.org.glassfish.jaxb是JAXB API的最新参考实现.使用下面的JAXB RI maven依赖将解决问题.

    <dependency>
        <groupId>org.glassfish.jaxb</groupId>
        <artifactId>jaxb-runtime</artifactId>
        <version>2.2.11</version>
    </dependency>

Answer 3

我发现的最佳解决方案是使用 maven-jaxb2-plugin，那么您需要的唯一依赖项是：

    <!-- https://mvnrepository.com/artifact/org.jvnet.jaxb2.maven2/maven-jaxb2-plugin -->
    <dependency>
        <groupId>org.jvnet.jaxb2.maven2</groupId>
        <artifactId>maven-jaxb2-plugin</artifactId>
        <version>0.14.0</version>
    </dependency>