JAVA使用JAXB规范读取XML转化为POJO

1.引入相关依赖

JDK 11，language level 11

1.lombok

implementation group: 'org.projectlombok', name: 'lombok', version: '1.18.24'
annotationProcessor 'org.projectlombok:lombok:1.18.24'

2.jaxb依赖

implementation group: 'javax.xml.bind', name: 'jaxb-api', version: '2.3.0'
implementation group: 'com.sun.xml.bind', name: 'jaxb-core', version: '2.3.0'
implementation group: 'com.sun.xml.bind', name: 'jaxb-impl', version: '2.3.0'
implementation group: 'xerces', name: 'xercesImpl', version: '2.12.2'
implementation group: 'javax.activation', name: 'activation', version: '1.1.1'

3.springboot相关依赖

springboot-plugin

buildscript {
    repositories {
        mavenCentral()
        maven { url 'https://maven.aliyun.com/nexus/content/repositories/google' }
        maven { url 'https://maven.aliyun.com/nexus/content/groups/public' }
        maven { url 'https://maven.aliyun.com/nexus/content/repositories/jcenter' }

    }
    dependencies{
        // springboot plugin used to generate jar
        classpath("org.springframework.boot:spring-boot-gradle-plugin:2.6.6")
    }
}
apply plugin: "java"
apply plugin: "org.springframework.boot"

springboot starter

implementation group: 'org.springframework.boot', name: 'spring-boot-starter-web', version: '2.6.6'

2.JAXB转xml为java bean详解

2.1 bean和节点对应关系

定义的java bean需要用@XmlRootElement(name = "<value>")注解来对应xml节点，比如bean 【ProductSeriesModel】和xml节点 <ProductSeries></ProductSeries>对应，那么bean 【ProductSeriesModel】就需要使用@XmlRootElement(name = "ProductSeries")注解。

2.2 定义bean内那些属性需要和xml节点mapping

bean用@XmlAccessorType(XmlAccessType.<>)说明本类中的属性那些需要和xml的节点mapping起来，一般用@XmlAccessorType(XmlAccessType.FIELD)。

2.3 定义xml 节点包含子节点

如果xml的标签ProductSeries内部包含了标签Product，且标签ProductSeries对应bean ProductSeriesModel，标签Product对应bean ProductModel，那么就在ProductSeries的一个ProductModel类型的属性上使用@XmlElement(name = "Product")表明包含标签ProductSeries包含标签Product。

2.4 定义xml节点的属性

如果xml标签Field有属性name，且该Field标签和bean ProductFieldModel对应，则就在ProductFieldModel的一个属性上使用@XmlAttribute(name="name")表明：该属性和Field标签的name属性对应。

2.5 bean定义注意事项

1. bean的所有属性命名要符合java bean命令规范，即小写开头、驼峰命名，且不要用is这种开头。
2. 所有bean应有无参和包含所有参数的构造方法，所以使用lombok的@AllArgsConstructor、@NoArgsConstructor
3. bean的所有需要和xml mapping的属性应该有getter、setter，所以使用lombok的@Data

3.例子

3.1 xml文本例子

<?xml version="1.0" encoding="UTF-8" ?>
<ProductSeries defaultClass="cbf.cdb.data.ProductSeriesA">
    <FieldGroup id="MessageHeader">
        <Field sequence="1" length="1" name="filedA" dataType="string"/>
        <Field sequence="1" length="1" name="filedB" dataType="string"/>
        <Field sequence="3" length="2" name="filedC" dataType="string"/>
        <Field sequence="4" length="3" name="filedD" dataType="string" offset="1"/>
        <Field sequence="7" length="8" name="filedE" dataType="datetime" format="yyyyMMddHHmmss" dBFormat="yyyy-MM-dd HH:mm:ss"/>
    </FieldGroup>
    <Product name="Product1" category="C" type="I">
        <FieldGroup sequence="0"  name="Header" referenceId="MessageHeader"/>
    </Product>
    <Product name="Product2" category="C" type="M">
        <FieldGroup sequence="0" name="Header" referenceId="MessageHeader"/>
        <FieldGroup sequence="1" name="Label">
            <Field sequence="1" length="14" name="S1" dataType="string"/>
            <Field sequence="2" length="09" name="c1" dataType="string"/>
            <Field sequence="3" length="12" name="b1" dataType="string"/>
            <Field sequence="4" length="05" name="p1" dataType="string" comment="sUB-Product type"/>
        </FieldGroup>
        <FieldGroup sequence="2" name="Label1">
            <Field sequence="1" length="08" name="o1" dataType="datetime" format="yyyyMMdd" dBFormat="MM-dd-yyyy"/>
        </FieldGroup>
        <FieldGroup sequence="3" name="Label2">
            <Field sequence="1" length="01" name="Q1" dataType="string"/>
            <Field sequence="2" length="14" name="Q2" dataType="double"/>
            <Field sequence="3" length="11" name="Q3" dataType="double?"/>
            <Field sequence="4" length="01" name="Q4" dataType="string"/>
            <Field sequence="5" length="01" name="Q5" dataType="string"/>
            <Field sequence="6" length="01" name="Q6" dataType="string"/>
            <Field sequence="7" length="01" name="Q7" dataType="string"/>
            <Field sequence="8" length="14" name="Q8" dataType="datetime" format="yyyyMMMddHHmmss" dBFormat="yyyy-MM-dd HH:mm:ss"/>
            <Field sequence="9" length="02" name="Q9" dataType="string"/>
            <Field sequence="10" length="01" name="Q10" dataType="string" offset="2"/>
        </FieldGroup>
        <FieldGroup sequence="4" name="Label3">
            <Field sequence="1" length="1" name="ChangeIndicator" dataType="int?"/>
        </FieldGroup>
    </Product>
</ProductSeries>

3.2  java bean定义

ProductFieldGroupModel

package com.bofan.xml_to_bean;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import javax.xml.bind.annotation.*;
import java.util.List;

/**
 * @Author yingge
 * @Date 2022/11/15 21:05
 */
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "FieldGroup")
@Data
@AllArgsConstructor
@NoArgsConstructor
public class ProductFieldGroupModel {
    @XmlAttribute
    private String name;
    @XmlAttribute
    private String id;
    @XmlAttribute
    private String referenceId;
    @XmlElement(name = "Field")
    private List<ProductFieldModel> fieldModelList;
}

ProductFieldModel

package com.bofan.xml_to_bean;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;

/**
 * @Author yingge
 * @Date 2022/11/15 21:06
 */
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "Field")
@Data
@AllArgsConstructor
@NoArgsConstructor
public class ProductFieldModel {
    @XmlAttribute
    private String name;
    @XmlAttribute
    private String dataType;
    @XmlAttribute
    private String format;
    @XmlAttribute
    private Integer sequence;
    @XmlAttribute
    private Integer length;
}

ProductModel

package com.bofan.xml_to_bean;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.apache.commons.lang3.StringUtils;

import javax.xml.bind.annotation.*;
import java.util.List;

/**
 * @Author yingge
 * @Date 2022/11/15 21:12
 */
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "Product")
@Data
@AllArgsConstructor
@NoArgsConstructor
public class ProductModel {
    @XmlAttribute
    private String name;
    @XmlAttribute
    private String category;
    @XmlAttribute
    private String type;
    @XmlElement(name = "FieldGroup")
    private List<ProductFieldGroupModel> productFieldGroupModels;
    private List<ProductFieldModel> productSortedFieldModels;

    /**
     * 将product里引用的 ProductFieldGroup 里的fields和自己定义的fields都塞到sortedMethods,
     * 按照 sequence 定义的顺序排序：首先 ProductFieldGroup 级别的 sequence 排序，然后 ProductFieldGroup 内的
     * sequence排序
     * @param referenceProductFieldGroupModelList
     */
    public void initFieldsWithReferenceFieldGroups(List<ProductFieldGroupModel> referenceProductFieldGroupModelList) throws Exception {
        if(this.productFieldGroupModels == null ||  this.productFieldGroupModels.size()<1){
            this.productSortedFieldModels = null;
            return;
        }
        // 迭代当前Product的每个filedGroup
        for(ProductFieldGroupModel currentFieldGroupModel: this.productFieldGroupModels){
            if(StringUtils.isNotBlank(currentFieldGroupModel.getReferenceId())){
                // fieldGroup不能同时包含 referenceId 和 fields
                if(currentFieldGroupModel.getFieldModelList()!=null && currentFieldGroupModel.getFieldModelList().size()>0){
                    throw new Exception(String.format("referenceId=%s,不能同时包含 referenceId和fields", currentFieldGroupModel.getReferenceId()));
                }
                // 在可引用的所有 FieldGroup中找到和当前 FieldGroup匹配的哪个
                ProductFieldGroupModel foundReferenceGroup = referenceProductFieldGroupModelList.stream().filter(referenceFieldGroup -> StringUtils.equals(currentFieldGroupModel.getReferenceId(), referenceFieldGroup.getId()))
                        .findFirst().orElse(null);
                if(foundReferenceGroup==null){
                    throw new Exception(String.format("找不到referenceId=%s的FieldGroup",currentFieldGroupModel.getReferenceId()));
                }
                // 把 reference FieldGroup中的所有字段放到当前的 fieldGroup中
                currentFieldGroupModel.setFieldModelList(foundReferenceGroup.getFieldModelList());
            }
        }
    }
}

ProductSeriesModel

package com.bofan.xml_to_bean;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.xml.bind.annotation.*;
import java.util.List;

/**
 * @Author yingge
 * @Date 2022/11/15 21:10
 */
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "ProductSeries")
@Data
@AllArgsConstructor
@NoArgsConstructor
public class ProductSeriesModel {
    @XmlElement(name = "FieldGroup")
    private List<ProductFieldGroupModel> productFieldGroupModels;
    @XmlElement(name="Product")
    private List<ProductModel> productModels;

    public void Init() throws Exception {
        if(productModels!=null && productModels.size()<=0){
            return;
        }
        for(ProductModel productModel: productModels){
            productModel.initFieldsWithReferenceFieldGroups(productFieldGroupModels);
        }
    }
}

3.3 xml to bean代码

XmlParserUtil

package com.bofan.xmlparse;

import com.bofan.xml_to_bean.ProductSeriesModel;
import org.springframework.context.annotation.Conditional;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Unmarshaller;
import java.io.*;

/**
 * @Author yingge
 * @Date 2022/11/19 1:51
 */
public class XmlParserUtil {
    public static void main(String[] args) {
        testXmlToBean();
    }
    public static void testXmlToBean(){
        try {
            ProductSeriesModel productSeriesModel = deserializeFromXmlToPOJO(ProductSeriesModel.class, "/ProductSeries1.xml");
            System.out.println(productSeriesModel.toString());
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    private static Object xmlStrToOject(Class<?> clazz, String xmlStr) throws Exception {
        Object xmlObject = null;
        Reader reader = null;
        JAXBContext context = JAXBContext.newInstance(clazz);
        // XML 转为对象的接口
        Unmarshaller unmarshaller = context.createUnmarshaller();
        reader = new StringReader(xmlStr);
        //以文件流的方式传入这个string
        xmlObject = unmarshaller.unmarshal(reader);
        if (null != reader) {
            reader.close();
        }
        return xmlObject;
    }

    /**
     * convert to stream from configFilePath to the java bean typed clazz
     * @param clazz
     * @param configFilePath
     * @return
     * @param <T>
     * @throws Exception
     */
    public static <T> T deserializeFromXmlToPOJO(Class<T> clazz, String configFilePath) throws Exception {
        Resource resource = new ClassPathResource(configFilePath);
        BufferedReader br = new BufferedReader(new InputStreamReader(resource.getInputStream(), "utf-8"));
        StringBuffer buffer = new StringBuffer();
        String line = "";
        while((line = br.readLine())!=null){
            buffer.append(line);
        }
        br.close();
        // convert xml file to java bean
        return (T)xmlStrToOject(clazz, buffer.toString());
    }
}

3.4 测试

在testXmlToBean()的sout处打断点，得出bean的信息如下

3.5 注意

不要给常量类加上lombok的@NoArgsConstructor注解额，否则会报错

public class ProductFieldType {
    public final static String String_ = "string";
    public final static String Int_ = "int";
    public final static String NullableInt = "int?";
    public final static String Double_ = "double";
    public final static String NullableDouble = "double";
    public final static String DateTime_ = "datetime";
    public final static String NullableDateTime_ = "datetime";
}

参考：Springboot中使用Xstream进行XML与Bean 相互转换-阿里云开发者社区

4.code 

JavaForOpen/XmlParserUtil.java at main · cbfsuper/JavaForOpen · GitHub