XMLEncoder - 运行时异常答案

【问题标题】：XMLEncoder - Runtime ExceptionXMLEncoder - 运行时异常
【发布时间】：2013-04-06 23:51:30
【问题描述】：

我一直在玩 java 中的序列化 XML，但有点卡住了。当我运行这个程序时，我得到了两个异常，我不确定原因是什么：

java.lang.InstantiationException: Ship
Continuing ...
java.lang.Exception: XMLEncoder: discarding statement XMLEncoder.writeObject(Ship);
Continuing ...

我怀疑我尝试序列化的类有问题，因为当我使用互联网示例时，它工作正常。

谁能指出我犯了什么错误。

主要：

public class Main {

    private static final String XMLLocation = "xmlTest.xml";
    static ObjectSerializationToXML serializer = new ObjectSerializationToXML();

    public Main() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @param args
     * @throws Exception 
     */
    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        Ship ship = new Ship("name", "324");
        serializer.serializeObjectToXML(XMLLocation, ship);

    }

}

对象序列化-XML类：

import java.beans.XMLDecoder;
import java.beans.XMLEncoder;
import java.io.FileInputStream;
import java.io.FileOutputStream;

public class ObjectSerializationToXML {

    /**
     * <span id="IL_AD10" class="IL_AD">This method</span> saves (serializes) any java bean object into xml file
     */
    public void serializeObjectToXML(String xmlFileLocation,
            Object objectToSerialize) throws Exception {
        FileOutputStream os = new FileOutputStream(xmlFileLocation);
        XMLEncoder encoder = new XMLEncoder(os);
        encoder.writeObject(objectToSerialize);
        encoder.close();
    }

    /**
     * Reads Java Bean Object From XML File
     */
    public Object deserializeXMLToObject(String xmlFileLocation)
            throws Exception {
        FileInputStream os = new FileInputStream(xmlFileLocation);
        XMLDecoder decoder = new XMLDecoder(os);
        Object deSerializedObject = decoder.readObject();
        decoder.close();

        return deSerializedObject;
    }
}

要序列化的对象（导致异常的我的对象）：

public class Ship {

    private String name;
    private String yearBuilt;


    public Ship(String name, String yearBuilt) {
        this.name = name;
        this.yearBuilt = yearBuilt;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    public String getYearBuild() {
        return yearBuilt;
    }
    public void setYearBuild(String yearBuild) {
        this.yearBuilt = yearBuild;
    }
    @Override
    public String toString() {
        return "ship [name=" + name + ", yearBuilt=" + yearBuilt + "]";
    }

}

要序列化的对象（来自互联网的示例）：

public class MyBeanToSerialize {
    private String firstName;
    private String lastName;
    private int age;

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = 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;
    }

}

【问题讨论】：

我所做的问题是我需要一个默认构造函数并实现 java.io.Serializable。这两个步骤将使我的类 JavaBeans 兼容并且一切顺利！
public class Ship 实现 java.io.Serializable{ private String name;私有字符串 yearBuilt； public Ship(){ this.name = ""; this.yearBuilt = "0000"; } //代码 } }
干得好！现在请尝试创建一个喜欢并标记它的答案，它可能对其他人有所帮助。 :-)

标签： java xml class object serialization

【解决方案1】：

当任何包含参数化构造函数并试图序列化的类时，它应该只被默认构造函数实例化。所以，XMLEncoder 默认构造函数需要一个对象来序列化它。

Ship 类在包含参数化构造函数时必须实现默认构造函数，因为每当 Ship 类变为可序列化时，它都会寻找默认构造函数来实例化 XMLEncoder。

请根据以下找到更正的船级。

public class Ship {

private String name;
private String yearBuilt;


public Ship(String name, String yearBuilt) {
    this.name = name;
    this.yearBuilt = yearBuilt;
}

//Default constructor must be implemented for XMLEncoder serializing
public Ship() {
    super();
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}
public String getYearBuild() {
    return yearBuilt;
}
public void setYearBuild(String yearBuild) {
    this.yearBuilt = yearBuild;
}
@Override
public String toString() {
    return "ship [name=" + name + ", yearBuilt=" + yearBuilt + "]";
}

}

【讨论】：