DomHandler 为多条记录捕获文本答案

【问题标题】：DomHandler to capture text for multiple recordsDomHandler 为多条记录捕获文本
【发布时间】：2014-06-26 08:13:33
【问题描述】：

我正在尝试将 @XmlAnyElement 与 DomHandler 一起使用来捕获特定字段中的未解析文本，例如 Blaise Doughan 的 this 示例。但是，当我尝试解析多个客户时，所有先前记录中的 bio 字段的内容会继续发送到我的 DomHandler！

这是我要解析的示例文档：

<?xml version="1.0" encoding="UTF-8"?>
<customers>
   <customer>
     <name>Jane Doe</name>
     <bio>
       <html>Jane's bio</html>
     </bio>
   </customer>
   <customer>
     <name>John Doe</name>
     <bio>
       <html>John's bio</html>
     </bio>
   </customer>
</customers>

但是输出是：

 Name:  Jane Doe 
 Bio:   <html>Jane's bio</html>
 Name:  John Doe 
 Bio:   <html>Jane's bio</html>

BioHandler（与previous example保持不变）

package blog.domhandler;

import java.io.StringReader;
import java.io.StringWriter;

import javax.xml.bind.ValidationEventHandler;
import javax.xml.bind.annotation.DomHandler;
import javax.xml.transform.Source;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

public class BioHandler implements DomHandler<String, StreamResult> {

    private static final String BIO_START_TAG = "<bio>";
    private static final String BIO_END_TAG = "</bio>";

    private StringWriter xmlWriter = new StringWriter();

    public StreamResult createUnmarshaller(ValidationEventHandler errorHandler) {
        return new StreamResult(xmlWriter);
    }

    public String getElement(StreamResult rt) {
        String xml = rt.getWriter().toString();
        int beginIndex = xml.indexOf(BIO_START_TAG) + BIO_START_TAG.length();
        int endIndex = xml.indexOf(BIO_END_TAG);
        return xml.substring(beginIndex, endIndex);
    }

    public Source marshal(String n, ValidationEventHandler errorHandler) {
        try {
            String xml = BIO_START_TAG + n.trim() + BIO_END_TAG;
            StringReader xmlReader = new StringReader(xml);
            return new StreamSource(xmlReader);
        } catch(Exception e) {
            throw new RuntimeException(e);
        }
    }

}

客户（与previous example保持不变）

package blog.domhandler;

import javax.xml.bind.annotation.XmlAnyElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlRootElement
@XmlType(propOrder={"name", "bio"})
public class Customer {

    private String name;
    private String bio;

    public String getName() {
        return name;
    }

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

    @XmlAnyElement(BioHandler.class)
    public String getBio() {
        return bio;
    }

    public void setBio(String bio) {
        this.bio = bio;
    }

}

客户

package blog.domhandler;

import java.util.List;

import javax.xml.bind.annotation.XmlAnyElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlRootElement
public class Customers {

    private List<Customer> customers;

    public List<Customer> getCustomer() {
        return customers;
    }

    public void setCustomer(List<Customer> c) {
        this.customers = c;
    }

}

演示（驱动程序）

package blog.domhandler;

import java.io.File;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;

public class Demo {

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

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        Customers customers = (Customers) unmarshaller.unmarshal(new File("src/blog/domhandler/input.xml"));

        for( Customer customer: customers.getCustomer() ) {

        System.out.println("Name:  " + customer.getName());
        System.out.println("Bio:   " + customer.getBio());

        }

    }
}

当我在 BioHandler.getElement() 中放置断点时，我看到它第一次调用的 String xml 取值

<?xml version="1.0" encoding="UTF-8"?><bio><html>Jane's bio</html>
    </bio>

第二次调用String xml时取值

<?xml version="1.0" encoding="UTF-8"?><bio><html>Jane's bio</html>
    </bio><?xml version="1.0" encoding="UTF-8"?><bio><html>John's bio</html>
    </bio>

是否有某种方法可以向解析器指示在每次调用 BioHandler.getElement() 后应该丢弃该内容？

【问题讨论】：

标签： java xml jaxb

【解决方案1】：

原来我的问题已在blog 帖子的第一条评论中得到回答，该示例来自该帖子。 BioHandler.createUnmarshaller() 的代码应该是：

public StreamResult createUnmarshaller(ValidationEventHandler errorHandler) {
    xmlWriter.getBuffer().setLength(0);
    return new StreamResult(xmlWriter);
}

【讨论】：