根据XML生成实体类

　　因为对接系统的XML所需映射的实体类有几十个，自己来处理不太现实，于是一直找寻找这样的工具，终于让我发现了jaxb2-maven-plugin：

　　http://www.mojohaus.org/jaxb2-maven-plugin/Documentation/v2.2/

　　一键生成，使用也比较方便，但是需要在maven环境下，下面将介绍如果使用

　　在maven工程下的pom.xml导入：

             <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>jaxb2-maven-plugin</artifactId>
                <version>2.5.0</version>
                <executions>
                    <execution>
                        <id>id1</id>
                        <phase>generate-sources</phase>
                        <goals>
                            <goal>xjc</goal>
                        </goals>
                        <configuration>
                            <!-- XSD源文件 -->
                            <sources>
                                <source>src/main/xsd</source>
                            </sources>
                            <!-- 源码输出目录 -->
                            <outputDirectory>target/generated-sources/jaxb</outputDirectory>
                            <!-- 指定文件生产 -->
                            <!--<schemaFiles>client_centric_data.xsd</schemaFiles>-->
                            <packageName>com.zgz.adsr</packageName>
                        </configuration>
                    </execution>
                </executions>
                <!--<configuration>-->
                    <!--&lt;!&ndash; The package of your generated sources &ndash;&gt;-->
                    <!--<packageName>com.zgz</packageName>-->
                <!--</configuration>-->
            </plugin>

　　然后，在工程中是用mvn clean install就会生成源码了。

　　

　　如果有多个XSD文件，可以不指定packageName，会自动分类，如果指定了，就所有实体类都在一起了，挺不方便的。可能是不清楚怎么设置，有清楚怎么设置的，麻烦评论让我学习一下。

　　下面说说，映射父节点的东东，因为请求的XML父节点要设置前缀以及各种东东的，例如下图：

　　

　　可在生成的package-info.java文件中添加注解：

@javax.xml.bind.annotation.XmlSchema(
　　　　 // 注意这里，下面的XmlNs匹配了，就显示ie前缀
        namespace = "http://www.shkf.com/rootelement",
        //子节点的设置
        //elementFormDefault = javax.xml.bind.annotation.XmlNsForm.QUALIFIED,
        xmlns={ @XmlNs(prefix="ie", namespaceURI="http://www.xxx.com/rootelement"),
                @XmlNs(prefix="ie1", namespaceURI="http://www.xxx.com/subaccount"),
                @XmlNs(prefix="ie2", namespaceURI="http://www.xxx.com/ccd"),
                @XmlNs(prefix="simple", namespaceURI="http://www.xxx.com/simple"),
                @XmlNs(prefix="tcl", namespaceURI="http://www.xxx.com/tcl"),
                @XmlNs(prefix="xsi", namespaceURI="http://www.w3.org/2001/XMLSchema-instance")}
)

　　但是schemaLocation的设置就在请求实体转换为XML的时候做设置：

　　marshaller.setProperty(Marshaller.JAXB_SCHEMA_LOCATION, "http://www.xxx.com/rootelement root_elements.xsd ");

　　或者在父节点实体类加个属性值：

　　@XmlAttribute(name ="xsi:schemaLocation")

　　public String schemaLocation="http://www.xxx.com/rootelement root_elements.xsd ";

　　还有一种方式设置前缀，继承NamespacePrefixMapper，但跟着上面的属性设置，好像会有点问题，具体还没怎么研究。

　　使用这方式需要引用依赖，不然会报错。

        <dependency>
            <groupId>com.sun.xml.bind</groupId>
            <artifactId>jaxb-impl</artifactId>
            <version>2.2.4-1</version>
        </dependency>

　　如要去掉standalone，可参考：

　　https://stackoverflow.com/questions/14152523/remove-standalone-yes-from-jaxb-generated-xml

　　https://blog.csdn.net/weixin_39964562/article/details/79072277

import java.io.*;
import javax.xml.bind.*;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.stream.*;

@XmlRootElement
public class Login {

    private JAXBContext jaxbContext;
    private XMLOutputFactory xmlOutputFactory;

    public Login() {
        try {
            jaxbContext = JAXBContext.newInstance(Login.class);
            xmlOutputFactory = XMLOutputFactory.newFactory();
        } catch(Exception e) {
            e.printStackTrace();
        }

    }

    public static void main(String[] args) {
        Login demo = new Login();
        System.out.println(demo.getMessage());
    }

    public final String getMessage() {
        try {
            Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
            jaxbMarshaller.setProperty("jaxb.encoding", "ISO-8859-1");
            jaxbMarshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);

            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            XMLStreamWriter xmlStreamWriter = xmlOutputFactory.createXMLStreamWriter(baos, (String) jaxbMarshaller.getProperty(Marshaller.JAXB_ENCODING));
            xmlStreamWriter.writeStartDocument((String) jaxbMarshaller.getProperty(Marshaller.JAXB_ENCODING), "1.0");
            jaxbMarshaller.marshal(this, xmlStreamWriter);
            xmlStreamWriter.writeEndDocument();
            xmlStreamWriter.close();
            return new String(baos.toByteArray());
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }

}

　　JaxbUtil类：

package xxxx.util;


import com.sun.xml.bind.marshaller.NamespacePrefixMapper;
//import com.sun.xml.internal.bind.marshaller.NamespacePrefixMapper;
import org.apache.commons.lang.StringUtils;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;

import javax.xml.XMLConstants;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.transform.Source;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Validator;
import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;

/**
 * @author GuangZe
 * @version v1.0
 * @project: vedio
 * @description: 这里描述类的用处
 * @copyright: © 2020
 * @company:
 * @date 2020/12/16 15:00
 */
public class JaxbUtil {

    public static String validate(String xml, String xsdPath) {
        String errMsg = null;
        String[] xmlArr;
        int lineNum;
        try {
            Source root = new StreamSource(JaxbUtil.class.getClassLoader()
                    .getResourceAsStream("xsd/root_elements.xsd"));

            Source code = new StreamSource(JaxbUtil.class.getClassLoader()
                    .getResourceAsStream("xsd/code_lists.xsd"));

            Source simple = new StreamSource(JaxbUtil.class.getClassLoader()
                    .getResourceAsStream("xsd/simple_types.xsd"));

            Source ccd = new StreamSource(JaxbUtil.class.getClassLoader()
                    .getResourceAsStream("xsd/client_centric_data.xsd"));

            Source customer = new StreamSource(JaxbUtil.class.getClassLoader()
                    .getResourceAsStream("xsd/customer_account.xsd"));

            Source sub = new StreamSource(JaxbUtil.class.getClassLoader()
                    .getResourceAsStream("xsd/sub_account.xsd"));

            Source trade = new StreamSource(JaxbUtil.class.getClassLoader()
                    .getResourceAsStream("xsd/trading_account.xsd"));

            Source[] sourceArr = {code, simple, ccd, customer, sub, trade, root};

            Schema schema = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI).newSchema(sourceArr);
            Validator validator = schema.newValidator();
            Source s = new StreamSource(new StringReader(xml));
            validator.validate(s);
        }catch (SAXParseException e){
            e.printStackTrace();
            xmlArr = xml.split("
");
            lineNum = e.getLineNumber();
            errMsg = e.getMessage();
            if(lineNum<=xmlArr.length && StringUtils.isNotBlank(xmlArr[lineNum-1])){
                errMsg +="["+xmlArr[lineNum-1].trim()+"]";
            }
            System.out.println(errMsg);
        } catch (SAXException e1) {
            e1.printStackTrace();
            errMsg = e1.getMessage();
            System.out.println(errMsg);
        } catch (IOException e2) {
            e2.printStackTrace();
            errMsg = e2.getMessage();
            System.out.println(errMsg);
        }
        return errMsg;
    }

    /**
     * 序列化
     * @param object
     * @throws JAXBException
     */
    public static String marshall(Object object) throws JAXBException {
        // 通过映射的类创建XMLContext上下文对象，其中参数为映射的类。
        JAXBContext jaxbContext = JAXBContext.newInstance(object.getClass());
        // 通过JAXBComtext上下文对象的createMarshaller()方法，创建一个对象java格式转化成XML的格式
        Marshaller marshaller = jaxbContext.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");
        //自定义前缀
//        NamespacePrefixMapper mapper = new PreferredMapper();
//        marshaller.setProperty("com.sun.xml.bind.namespacePrefixMapper", mapper);
        marshaller.setProperty(Marshaller.JAXB_SCHEMA_LOCATION, "http://www.xxx.com/rootelement root_elements.xsd ");
        // 最后，将JAVA对象转换到制定的输出位置，其中的object为java对象。
        StringWriter writer = new StringWriter();
        marshaller.marshal(object, writer);
        return writer.toString();
    }

    /**
     * 解析
     * @param clazz
     * @param xml
     * @return
     * @throws Exception
     */
    public static Object unmarshaller(Class<?> clazz, String xml) throws Exception {
        if (StringUtils.isEmpty(xml)) {
            return null;
        }
        // 通过映射的类创建XMLComtext上下文对象，其中参数为映射的类。
        JAXBContext jaxbContext = JAXBContext.newInstance(clazz);
        // 通过JAXBContext上下文对象创建createUnmarshaller()方法，创建XML转换成JAVA对象的格式。
        Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
        // 最后，将XML转换成对映的类，转换后需要强制性转换成映射的类
        StringReader stringReader = new StringReader(xml);
        Object object = unmarshaller.unmarshal(stringReader);
        return object;
    }

    public static class PreferredMapper extends NamespacePrefixMapper {
        @Override
        public String getPreferredPrefix(String namespaceUri,
                                         String suggestion, boolean requirePrefix) {
            if ("http://www.xxx.com/rootelement".equals(namespaceUri)) {
                return "ie";
            }
            return suggestion;
        }

    }

}
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原文地址：https://www.cnblogs.com/zgz21/p/14150757.html