JAXB和构造函数 [英] JAXB and constructors

问题描述

我开始学习JAXB，所以我的问题可能很蠢。现在我有类并且想生成XML Schema。在此指示后，我得到例外

I'm starting learning JAXB, so my question can be very silly. Now I have classes and want generate XML Schema. Going after this instruction I get exception

IllegalAnnotationExceptions ...没有非arg默认的
构造函数。

IllegalAnnotationExceptions ... does not have a no-arg default constructor.

是啊。我的类没有默认没有arg的构造函数。太容易了。我有包可见构造函数/最终方法和偏离课程与参数的类。我应该做什么 - 创建一些特定的momemto / builder类或者指定我的构造函数到JAXB（以什么方式？）？感谢。

Yeah. My classes haven't default no-arg constructors. It's too easy. I have classes with package visible constructors / final methods and off course with arguments. What shall I do - create some specific momemto/builder classes or specify my constructors to JAXB (in what way?) ? Thanks.

推荐答案

JAXB可以使用XML适配器支持这种情况。考虑你有没有零arg参数构造函数的以下对象：

JAXB can support this case using an XML Adapter. Consider you have the following object with no zero-arg constructor:

package blog.immutable;

public class Customer {

    private final String name;
    private final Address address;

    public Customer(String name, Address address) {
        this.name = name;
        this.address = address;
    }

    public String getName() {
        return name;
    }

    public Address getAddress() {
        return address;
    }

}

您只需创建一个可映射此类的版本：

You simply need to create a mappable version of this class:

package blog.immutable.adpater;

import javax.xml.bind.annotation.XmlAttribute;
import blog.immutable.Address;

public class AdaptedCustomer {

    private String name;
    private Address address;

    @XmlAttribute
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

}

<他们：

And an XML Adapter to convert between them:

package blog.immutable.adpater;

import javax.xml.bind.annotation.adapters.XmlAdapter;
import blog.immutable.Customer;

public class CustomerAdapter extends XmlAdapter<AdaptedCustomer, Customer> {

    @Override
    public Customer unmarshal(AdaptedCustomer adaptedCustomer) throws Exception {
        return new Customer(adaptedCustomer.getName(), adaptedCustomer.getAddress());
    }

    @Override
    public AdaptedCustomer marshal(Customer customer) throws Exception {
        AdaptedCustomer adaptedCustomer = new AdaptedCustomer();
        adaptedCustomer.setName(customer.getName());
        adaptedCustomer.setAddress(customer.getAddress());
        return adaptedCustomer;
    }

}

Customer类，只需使用@XmlJavaTypeAdapter注释：

Then for properties that refer to the Customer class, simply use the @XmlJavaTypeAdapter annotation:

package blog.immutable;

import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
import blog.immutable.adpater.CustomerAdapter;

@XmlRootElement(name="purchase-order")
public class PurchaseOrder {

    private Customer customer;

    @XmlJavaTypeAdapter(CustomerAdapter.class)
    public Customer getCustomer() {
        return customer;
    }

    public void setCustomer(Customer customer) {
        this.customer = customer;
    }

} 

示例参见：

• http://bdoughan.blogspot.com/2010/12/jaxb-and-immutable-objects.html

• http://bdoughan.blogspot.com/2010/12/jaxb-and-immutable-objects.html

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