我是 JAXB 的新手，一开始我正在整理一些简单的 Java 文件，例如 Hello, world!。

我想编码整个文件，即使我的评论行是这样放置的:

/*
* some comment
*/

//another comment

并在注释 block 中以 XML 格式获取它们:

<!--
some comment
-->

<!-- another comment -->

有什么方法可以用注释编码 java 文件吗？

最佳答案

您的用例需要克服一些障碍:

1. 注释未存储在类的字节码中，因此您需要在其他地方提供它们。
2. JAXB API 不提供映射到内容节点的方法。

话虽如此，下面是一种可能适合您使用的方法:StAX 与 JAXB 并利用 Marshaller.Listener。

Java 模型

客户

import javax.xml.bind.annotation.*;

@XmlRootElement
@XmlType(propOrder={"name", "address"})
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {

    private String name;
    private Address address;

    public Customer() {
    }

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

}

地址

import javax.xml.bind.annotation.*;

@XmlAccessorType(XmlAccessType.FIELD)
public class Address {

    String street;

    public Address() {
    }

    public Address(String street) {
        this.street = street;
    }

}

演示代码

MyMarshalListener

import javax.xml.bind.Marshaller;
import javax.xml.stream.*;

public class MyMarshallerListener extends Marshaller.Listener {

    private XMLStreamWriter xsw;

    public  MyMarshallerListener(XMLStreamWriter xsw) {
        this.xsw = xsw;
    }

    @Override
    public void beforeMarshal(Object source)  {
        try {
            xsw.writeComment("Before:  " + source.toString());
        } catch(XMLStreamException e) {
            // TODO: handle exception
        }
    }

    @Override
    public void afterMarshal(Object source) {
        try {
            xsw.writeComment("After:  " + source.toString());
        } catch(XMLStreamException e) {
            // TODO: handle exception
        }
    }

}

演示

import javax.xml.bind.*;
import javax.xml.stream.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Customer.class);

        Address address = new Address("123 A Street");
        Customer customer = new Customer("Jane", address);

        XMLOutputFactory xof = XMLOutputFactory.newFactory();
        XMLStreamWriter xsw = xof.createXMLStreamWriter(System.out);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setListener(new MyMarshallerListener(xsw));
        marshaller.marshal(customer, xsw);
        xsw.close();;
    }

}

实际输出

<?xml version="1.0" ?><!--Before:  forum26802450.Customer@18de9738--><!--Before:  forum26802450.Customer@18de9738--><customer><name>Jane</name><!--Before:  forum26802450.Address@43e47e37--><address><street>123 A Street</street><!--After:  forum26802450.Address@43e47e37--></address><!--After:  forum26802450.Customer@18de9738--></customer><!--After:  forum26802450.Customer@18de9738-->

格式化输出

输出格式如下:

<?xml version="1.0" ?>
<!--Before:  forum26802450.Customer@18de9738-->
<!--Before:  forum26802450.Customer@18de9738-->
<customer>
    <name>Jane</name>
    <!--Before:  forum26802450.Address@43e47e37-->
    <address>
        <street>123 A Street</street>
        <!--After:  forum26802450.Address@43e47e37-->
    </address>
    <!--After:  forum26802450.Customer@18de9738-->
 </customer>
 <!--After:  forum26802450.Customer@18de9738-->

关于java - JAXB - 带有 java 注释的编码，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/26802450/