【开发心得】Jaxb使用珠玑
前言
Java操作xml转换成javaBean,或者javaBean转换为xml的方式有很多。常见的有dom4j等工具直接操作dom，或者使用jaxb.
jaxb介绍:
JAXB(Java Architecture for XML Binding简称JAXB)允许Java开发人员将Java类映射为XML表示方式。JAXB提供两种主要特性：将一个Java对象序列化为XML，以及反向操作，将XML解析成Java对象。换句话说，JAXB允许以XML格式存储和读取数据，而不需要程序的类结构实现特定的读取XML和保存XML的代码。
工具类
package com.test.tms.backend.service.utils;
import com.test.tms.backend.service.xml.ParseXmlExceptionHandler;
import com.sun.xml.internal.bind.marshaller.CharacterEscapeHandler;
import com.sun.xml.internal.bind.marshaller.NoEscapeHandler;
import com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl;
import com.sun.xml.internal.bind.v2.runtime.JaxBeanInfo;
import com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl;
import com.sun.xml.internal.bind.v2.util.XmlFactory;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.StringEscapeUtils;
import org.apache.commons.lang3.StringUtils;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import javax.xml.bind.*;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParserFactory;
import javax.xml.transform.sax.SAXSource;
import java.io.InputStream;
import java.io.StringWriter;
import java.nio.charset.StandardCharsets;
/**
* @Author: martin
* @Date: 2023/8/15 09:44
* @Description:
*/
@Slf4j
public class XMLUtils {
/**
* 将String类型的xml转换成对象
*/
public static Object convertXmlStrToObject(Class clazz, String xmlStr) {
Object xmlObject = null;
try {
JAXBContext context = JAXBContext.newInstance(clazz);
Unmarshaller unmarshaller = context.createUnmarshaller();
unmarshaller.setEventHandler(new ValidationEventHandler() {
@Override
public boolean handleEvent(ValidationEvent event) {
if (event.getSeverity() == 2) {
Throwable t = event.getLinkedException();
if (t != null) {
log.error(t.getMessage(), t);
}
return true;
}
return true;
}
});
InputStream inputStream = IOUtils.toInputStream(xmlStr, StandardCharsets.UTF_8);
InputSource inputSource = new InputSource(inputStream);
XMLReader reader = getXMLReader(context);
reader.setFeature("http://apache.org/xml/features/continue-after-fatal-error", true);
ParseXmlExceptionHandler errorHandler = new ParseXmlExceptionHandler();
reader.setErrorHandler(errorHandler);
SAXSource source = new SAXSource(reader, inputSource);
xmlObject = ((UnmarshallerImpl) unmarshaller).unmarshal0(source, (JaxBeanInfo) null);
} catch (Exception e) {
log.error(e.getMessage(), e);
}
return xmlObject;
}
public static XMLReader getXMLReader(JAXBContext context) throws JAXBException {
try {
SAXParserFactory parserFactory = XmlFactory.createParserFactory(((JAXBContextImpl) context).disableSecurityProcessing);
parserFactory.setValidating(false);
return parserFactory.newSAXParser().getXMLReader();
} catch (ParserConfigurationException var2) {
throw new JAXBException(var2);
} catch (SAXException var3) {
throw new JAXBException(var3);
}
}
/**
* @param javaBean
* @param <T>
* @return
* @description: 将包含@XmlRootElement的jaxb javaBean转换Xml
*/
public static <T> String javaBeanToXmlStr(T javaBean, Boolean noHeadFlag, Boolean keepSpecCharFlag) {
try {
JAXBContext context = JAXBContext.newInstance(javaBean.getClass());
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
// 去掉报文头
if (noHeadFlag) {
marshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);
}
// 禁止转义
if (keepSpecCharFlag) {
CharacterEscapeHandler escapeHandler = NoEscapeHandler.theInstance;
marshaller.setProperty("com.sun.xml.internal.bind.characterEscapeHandler", escapeHandler);
}
StringWriter writer = new StringWriter();
marshaller.marshal(javaBean, writer);
return writer.toString();
} catch (Exception e) {
log.error(e.getMessage(), e);
}
return null;
}
/**
* @param str
* @return
* @description: 将xml字符串进行加密
*/
public static String escapeXmlStr(String str) {
if (StringUtils.isNotBlank(str)) {
String escapedData = StringEscapeUtils.escapeXml11(str);
return escapedData;
}
return null;
}
}
珠玑
聊点心得:
1. 关于jaxb实体类的快速生成。
可以借助jxc或者 jdk自带tools，参考博主另一篇博文
参考如下设置:
JAXBContext context = JAXBContext.newInstance(javaBean.getClass());
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
// 去掉报文头
if (noHeadFlag) {
marshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);
}
3. 控制是否需要转义字符
jaxb控制字符转义，jaxb不转义字符。如下
// 禁止转义
if (keepSpecCharFlag) {
CharacterEscapeHandler escapeHandler = NoEscapeHandler.theInstance;
marshaller.setProperty("com.sun.xml.internal.bind.characterEscapeHandler", escapeHandler);
}
StringWriter writer = new StringWriter();
marshaller.marshal(javaBean, writer);
return writer.toString();有资料显示设置如下参数即可。
com.sun.xml.bind.characterEscapeHandler
但是实际上，java1.8 (331) 是
com.sun.xml.internal.bind.characterEscapeHandler
暂时没有去探究哪个版本开始变更的，遇到这种情况，直接翻一下源码即可。
它总共有4个实现类，如果不满足你的需求，可以手动实现并且替换即可。
4. 单独转义特殊字符。
实际上jaxb对于特殊字符的转义，默认不包含引号，这里使用StringEscapeUtils.escapeXml11()进行转义。
String escapedData = StringEscapeUtils.escapeXml11(str);
return escapedData;总结: 主要在实际开发中遇到了"JAXB嵌套，其中一个字段为String，存储的是xml"的情况。
