Java uses Xstream annotations to generate and parse xml

The article is reprinted from: https://blog.csdn.net/vampire2777/article/details/70915349

1. Introduction to Xstream; 

Usage restrictions: JDK version cannot be < 1.5. 
Although preprocessing annotations is safe, auto-detection annotations may cause race conditions. 
Features: 
simplified API; 
no mapping files; 
high performance, low memory footprint; 
clean XML; 
no modification required Object; supports internal private fields, does not require setter/getter methods, final fields; non-public classes, inner classes; classes do not require default constructors, full object graph support. Maintain object reference counts, circular references. i 
provide serialization interface; 
Custom conversion type strategy; 
detailed error diagnostics; 
fast output format; currently supports JSON and morphing.

Use Scene 
Transport Convert 
Persistence Persistence Object 
Configuration Configure 
Unit Tests Unit Test

2. Common knowledge of Xstream annotation: 
@XStreamAlias(“message”) Alias ​​annotation 
target: class, field 
@XStreamImplicit implicit collection 
@XStreamImplicit(itemFieldName=”part”) 
target: collection field 
@XStreamConverter(SingleValueCalendarConverter.class) injection conversion
Action target: Object  @XStreamAsAttribute is converted 
to attribute 
Action target: Field 
@XStreamOmitField Ignore field 
Action target: Field 
Auto-detect Annotations Automatically detect annotations 
xstream.autodetectAnnotations(true); 
Automatically detect annotations with XStream.processAnnotations(Class[] cls) The difference is performance. The auto-detection annotation will cache the type of all classes.

1. [Code] 1. Entity class: PersonBean

import java.util.List;

import com.thoughtworks.xstream.annotations.XStreamAlias;
import com.thoughtworks.xstream.annotations.XStreamImplicit;


@XStreamAlias("person")
public class PersonBean {
    @XStreamAlias("firstName")
    private String firstName;
    @XStreamAlias("lastName")
    private String lastName;

    @XStreamAlias("telphone")
    private PhoneNumber tel;
    @XStreamAlias("faxphone")
    private PhoneNumber fax;

    //测试一个标签下有多个同名标签
    @XStreamAlias("friends")
    private Friends friend;

    //测试一个标签下循环对象
    @XStreamAlias("pets")
    private Pets pet;


    //省略setter和getter
}

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10
• 11
• 12
• 13
• 14
• 15
• 16
• 17
• 18
• 19
• 20
• 21
• 22
• 23
• 24
• 25
• 26
• 27
• 28
• 29

2. [Code] 2. Entity class: PhoneNumber

@XStreamAlias("phoneNumber")
    public  class PhoneNumber{
        @XStreamAlias("code")
        private int code;
        @XStreamAlias("number")
        private String number;

            //省略setter和getter

    }

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10

3. [Code] 3. Entity class: Friends (there are multiple labels with the same name under one label)

**
     * 用Xstream注解的方式实现：一个标签下有多个同名标签 
     *@ClassName:Friends
     *@Description:TODO 5个name 中国，美国，俄罗斯，英国，法国
     *http://blog.csdn.net/menhuanxiyou/article/details/5426765
     */
    public static class Friends{
        @XStreamImplicit(itemFieldName="name")   //itemFieldName定义重复字段的名称，
        /*<friends>                               <friends>
            <name>A1</name>                         <String>A1</String>
            <name>A2</name>    如果没有，则会变成    =====>       <String>A1</String>
            <name>A3</name>                         <String>A1</String>
        </friends>                                </friends>
      */
        private List<String> name;

        public List<String> getName() {
            return name;
        }

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

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10
• 11
• 12
• 13
• 14
• 15
• 16
• 17
• 18
• 19
• 20
• 21
• 22
• 23
• 24

4. [Code] 4.1 Entity class: Animal (loop object entity 1 under the same label)

//测试同一标签下循环某一对象
    public  class Animal{
        @XStreamAlias("name")
        private String name;
        @XStreamAlias("age")
        private int age;
        public Animal(String name,int age){
            this.name=name;
            this.age=age;
        }

              //省略setter和getter
    }

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10
• 11
• 12
• 13

5. [Code] 4.2 Entity class: Pets (loop object entity 2 under the same label)

/**
     * 测试同一标签下循环某一对象
     *@ClassName:Pets
     *@Description:TODO
     */
    public class Pets{
        @XStreamImplicit(itemFieldName="pet")
        private List<Animal> animalList;

        public List<Animal> getAnimalList() {
            return animalList;
        }

        public void setAnimalList(List<Animal> animalList) {
            this.animalList = animalList;
        }

    }

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10
• 11
• 12
• 13
• 14
• 15
• 16
• 17
• 18

6. [Code] 5.Main function example 1: toxml

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.json.JsonWriter.Format;
import com.thoughtworks.xstream.io.xml.DomDriver;

/**
 *@ClassName:PersonTest
 *@Description:TODO 
 */
public class PersonTest {

    /** 
     * @Title: main 
     * @Description: TODO 
     * @param args 
     * @return void  
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub

        PersonBean per=new PersonBean();
        per.setFirstName("chen");
        per.setLastName("youlong");

        PhoneNumber tel=new PhoneNumber();
        tel.setCode(137280);
        tel.setNumber("137280968");

        PhoneNumber fax=new PhoneNumber();
        fax.setCode(20);
        fax.setNumber("020221327");
        per.setTel(tel);
        per.setFax(fax);


        //测试一个标签下有多个同名标签
        List<String> friendList=new ArrayList<String>();
        friendList.add("A1");
        friendList.add("A2");
        friendList.add("A3");
        Friends friend1=new Friends();
        friend1.setName(friendList);
        per.setFriend(friend1);

        //测试一个标签下循环对象
        Animal dog=new Animal("Dolly",2);
        Animal cat=new Animal("Ketty",2);
        List<Animal> petList=new ArrayList<Animal>();
        petList.add(dog);
        petList.add(cat);
        Pets pet=new Pets();
        pet.setAnimalList(petList);
        per.setPet(pet);

                    //java对象转换成xml
        String xml=XmlUtil.toXml(per);
        System.out.println("xml==="+xml);

    }
}

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10
• 11
• 12
• 13
• 14
• 15
• 16
• 17
• 18
• 19
• 20
• 21
• 22
• 23
• 24
• 25
• 26
• 27
• 28
• 29
• 30
• 31
• 32
• 33
• 34
• 35
• 36
• 37
• 38
• 39
• 40
• 41
• 42
• 43
• 44
• 45
• 46
• 47
• 48
• 49
• 50
• 51
• 52
• 53
• 54
• 55
• 56
• 57
• 58
• 59

7. [代码]xml效果图

xml===<person>
  <firstName>chen</firstName>
  <lastName>youlong</lastName>
  <telphone>
    <code>137280</code>
    <number>137280968</number>
  </telphone>
  <faxphone>
    <code>20</code>
    <number>020221327</number>
  </faxphone>
  <friends>
    <name>A1</name>
    <name>A2</name>
    <name>A3</name>
  </friends>
  <pets>
    <pet>
      <name>doly</name>
      <age>2</age>
    </pet>
    <pet>
      <name>Ketty</name>
      <age>2</age>
    </pet>
  </pets>
</person>

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10
• 11
• 12
• 13
• 14
• 15
• 16
• 17
• 18
• 19
• 20
• 21
• 22
• 23
• 24
• 25
• 26
• 27

8. [代码]5.2 main函数示例2：toBean

public static void main(String[] args) {
        // TODO Auto-generated method stub

        //toXml
//      String xmlStr=new PersonTest().toXml();

        //toBean
//      PersonBean per=new PersonTest().toBean();
        String xmlStr="<person>"+
                  "<firstName>chen</firstName>"+
                  "<lastName>youlong</lastName>"+
                  "<telphone>"+
                    "<code>137280</code>"+
                    "<number>137280968</number>"+
                  "</telphone>"+
                  "<faxphone>"+
                    "<code>20</code>"+
                    "<number>020221327</number>"+
                  "</faxphone>"+
                  "<friends>"+
                    "<name>A1</name>"+
                    "<name>A2</name>"+
                    "<name>A3</name>"+
                  "</friends>"+
                  "<pets>"+
                    "<pet>"+
                      "<name>doly</name>"+
                      "<age>2</age>"+
                    "</pet>"+
                    "<pet>"+
                      "<name>Ketty</name>"+
                      "<age>2</age>"+
                    "</pet>"+
                  "</pets>"+
                "</person>";
//用泛型的知识
        PersonBean person=XmlUtil.toBean(xmlStr, PersonBean.class);
        System.out.println("person=firstname=="+person.getFirstName());
        System.out.println("person==Friends==name1=="+person.getFriend().getName().get(0));
        System.out.println("person==Pets==name2=="+person.getPet().getAnimalList().get(1).getName());

/*
//效果与以下方法类同,(以下代码较为直观)
XStream xstream=new XStream(new DomDriver()); //注意：不是new Xstream(); 否则报错：

        xstream.processAnnotations(PersonBean.class);
        PersonBean person=(PersonBean)xstream.fromXML(xmlStr);
        System.out.println("person=firstname=="+person.getFirstName());
        System.out.println("person==Friends==name1=="+person.getFriend().getName().get(0));
        System.out.println("person==Pets==name=="+person.getPet().getAnimalList().get(1).getName());
*/


    }

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10
• 11
• 12
• 13
• 14
• 15
• 16
• 17
• 18
• 19
• 20
• 21
• 22
• 23
• 24
• 25
• 26
• 27
• 28
• 29
• 30
• 31
• 32
• 33
• 34
• 35
• 36
• 37
• 38
• 39
• 40
• 41
• 42
• 43
• 44
• 45
• 46
• 47
• 48
• 49
• 50
• 51
• 52
• 53
• 54

9. [代码]6.XmlUtil工具类（toxml（）和toBean（））

/**
     * 输出xml和解析xml的工具类
     *@ClassName:XmlUtil
     *@Description:TODO
     */
    public class XmlUtil{
        /**
         * java 转换成xml
         * @Title: toXml 
         * @Description: TODO 
         * @param obj 对象实例
         * @return String xml字符串
         */
        public static String toXml(Object obj){
            XStream xstream=new XStream();
//          XStream xstream=new XStream(new DomDriver()); //直接用jaxp dom来解释
//          XStream xstream=new XStream(new DomDriver("utf-8")); //指定编码解析器,直接用jaxp dom来解释

            ////如果没有这句，xml中的根元素会是<包.类名>；或者说：注解根本就没生效，所以的元素名就是类的属性
            xstream.processAnnotations(obj.getClass()); //通过注解方式的，一定要有这句话
            return xstream.toXML(obj);
        }

        /**
         *  将传入xml文本转换成Java对象
         * @Title: toBean 
         * @Description: TODO 
         * @param xmlStr
         * @param cls  xml对应的class类
         * @return T   xml对应的class类的实例对象
         * 
         * 调用的方法实例：PersonBean person=XmlUtil.toBean(xmlStr, PersonBean.class);
         */
        public static <T> T  toBean(String xmlStr,Class<T> cls){
            //注意：不是new Xstream(); 否则报错：java.lang.NoClassDefFoundError: org/xmlpull/v1/XmlPullParserFactory
            XStream xstream=new XStream(new DomDriver());
            xstream.processAnnotations(cls);
            T obj=(T)xstream.fromXML(xmlStr);
            return obj;         
        } 

       /**
         * 写到xml文件中去
         * @Title: writeXMLFile 
         * @Description: TODO 
         * @param obj 对象
         * @param absPath 绝对路径
         * @param fileName  文件名
         * @return boolean
         */

        public static boolean toXMLFile(Object obj, String absPath, String fileName ){
            String strXml = toXml(obj);
            String filePath = absPath + fileName;
            File file = new File(filePath);
            if(!file.exists()){
                try {
                    file.createNewFile();
                } catch (IOException e) {
                    log.error("创建{"+ filePath +"}文件失败!!!" + Strings.getStackTrace(e));
                    return false ;
                }
            }// end if 
            OutputStream ous = null ;
            try {
                ous = new FileOutputStream(file);
                ous.write(strXml.getBytes());
                ous.flush();
            } catch (Exception e1) {
                log.error("写{"+ filePath +"}文件失败!!!" + Strings.getStackTrace(e1));
                return false;
            }finally{
                if(ous != null )
                    try {
                        ous.close();
                    } catch (IOException e) {
                        log.error("写{"+ filePath +"}文件关闭输出流异常!!!" + Strings.getStackTrace(e));
                    }
            }
            return true ;
        }

        /**
         * 从xml文件读取报文
         * @Title: toBeanFromFile 
         * @Description: TODO 
         * @param absPath 绝对路径
         * @param fileName 文件名
         * @param cls
         * @throws Exception 
         * @return T
         */
        public static <T> T  toBeanFromFile(String absPath, String fileName,Class<T> cls) throws Exception{
            String filePath = absPath +fileName;
            InputStream ins = null ;
            try {
                ins = new FileInputStream(new File(filePath ));
            } catch (Exception e) {
                throw new Exception("读{"+ filePath +"}文件失败！", e);
            }

            String encode = useEncode(cls);
            XStream xstream=new XStream(new DomDriver(encode));
            xstream.processAnnotations(cls);
            T obj =null;
            try {
                obj = (T)xstream.fromXML(ins);
            } catch (Exception e) {
                // TODO Auto-generated catch block
                throw new Exception("解析{"+ filePath +"}文件失败！",e);
            }
            if(ins != null)
                ins.close();
            return obj;         
        } 

    }