用Apache Commons Betwixt2 在XML与Java对象之间相互转换

10年前
如果你需要做XML与Java对象之间相互转换,apache betwixt2是一个不二的选择。
 
官方主页:[url]http://commons.apache.org/betwixt/[/url]  目前最新版本是0.8.
 
以前我用XStream,但是对比起来还是没apache betwixt2来得容易。下面给些例子出来。
 
/**
* 测试Bean
*/

public class PersonBean {

        private String name;
        private int age;

        public PersonBean() {
        }

        public PersonBean(String name, int age) {
                this.name = name;
                this.age = age;
        }

        public String getName() {
                return name;
        }

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

        public int getAge() {
                return age;
        }

        public void setAge(int age) {
                this.age = age;
        }


        public String toString() {
                return "PersonBean{" +
                                "name='" + name + '\'' +
                                ", age=" + age +
                                '}';
        }
}
 
import java.io.StringReader;

import org.apache.commons.betwixt.io.BeanReader;

/**
* XML转Java
*/

public class ReadExampleApp {

        public static final void main(String args[]) throws Exception {

                //创建一个读取xml文件的流
                StringReader xmlReader = new StringReader(
                                "<?xml version='1.0' ?><person><age>25</age><name>James Smith</name></person>");

                //创建一个BeanReader实例,相当于转换器
                BeanReader beanReader = new BeanReader();

                //配置BeanReader实例
                beanReader.getXMLIntrospector().getConfiguration().setAttributesForPrimitives(false);
                beanReader.getBindingConfiguration().setMapIDs(false); //不自动生成ID

                //注册要转换对象的类,并指定根节点名称
                beanReader.registerBeanClass("person", PersonBean.class);

                //将XML解析Java Object
                PersonBean person = (PersonBean) beanReader.parse(xmlReader);

                //在控制台输出对象
                System.out.println(person);
        }
}
 
运行结果:
PersonBean{name='James Smith', age=25}

Process finished with exit code 0
 
import betwixt.Person;
import org.apache.commons.betwixt.io.BeanWriter;
import org.xml.sax.SAXException;

import java.beans.IntrospectionException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.StringWriter;
import java.util.Collection;

/**
* 将java对象转换为xml,并输出到文件
*/

public class WriteExampleApp {

        public static final void main(String [] args) throws Exception {

                //创建一个输出流,将用来输出Java转换的XML文件
                FileWriter outputWriter = new FileWriter("c:\\tttttttttt.txt");

                //输出XML的文件头
                outputWriter.write("<?xml version='1.0' ?>");

                //创建一个BeanWriter实例,并将BeanWriter的输出重定向到指定的输出流
                BeanWriter beanWriter = new BeanWriter(outputWriter);

                //配置BeanWriter对象
                beanWriter.getXMLIntrospector().getConfiguration().setAttributesForPrimitives(false);
                beanWriter.getBindingConfiguration().setMapIDs(false);
                beanWriter.enablePrettyPrint();

                Person person = new Person("阿牛", 21);
                beanWriter.write(person);

                //关闭输出流
                outputWriter.close();
        }
}
 
运行结果:

Process finished with exit code 0
(在C盘目录下创建一个名叫tttttttttt.txt的文件。
 
import betwixt.Person;
import org.apache.commons.betwixt.io.BeanWriter;

import java.io.StringWriter;

/**
* 将Java对象转换为XML,并获取其字符串
*
* @author leizhimin 2008-9-18 14:36:49
*/

public class WriteStringExampleApp {
        public static final void main(String [] args) throws Exception {
                String reslutXml;

                //创建一个输出流,将用来输出Java转换的XML文件
                StringWriter outputWriter = new StringWriter();

                //输出XML的文件头
                outputWriter.write("<?xml version='1.0' ?>");

                //创建一个BeanWriter实例,并将BeanWriter的输出重定向到指定的输出流
                BeanWriter beanWriter = new BeanWriter(outputWriter);

                //配置BeanWriter对象
                beanWriter.getXMLIntrospector().getConfiguration().setAttributesForPrimitives(false);
                beanWriter.getBindingConfiguration().setMapIDs(false);
                beanWriter.enablePrettyPrint();

                Person person = new Person("阿牛", 21);
                beanWriter.write(person);

                reslutXml = outputWriter.toString();

                //关闭输出流
                outputWriter.close();

                //控制台输出转换结果的字符串
                System.out.println(reslutXml);
        }
}
 
运行结果:
<?xml version='1.0' ?>    <Person>
        <addList/>
        <age>21</age>
        <name>阿牛</name>
    </Person>


Process finished with exit code 0
 
总结:
betwixt功能强大,使用简单,是快速开发不二的选择。
 
BeanWriter相当于一个双向转换器工厂,但是这个工厂需要装配,并且它是非线程安全的。
 
BeanWriter有很多配置项,可以将对象的成员装配成xml元素的属性。也可以改写元素属性的名字。默认情况下元素的名字与java成员的名字相同,根节点与java类名相同(不带包名)。并且这些操作是双向可逆的。太牛了吧!
 
BeanWriter还可以转换格式不规范的xml文档,比如节点无法有些不匹配,或者无法完全映射到对象上的xml,这些都不会出错,并且当节点为null的时候,转换也不用做特殊处理,非常简单。
 
BeanWriter在将Java转换为xml时,Java对象可以是复杂对象,对象之中嵌套对象,如果复杂对象的某个成员比如类型为另外一个对象为null时,还可以选择是否在生成xml的时候输出该节点。如果期望输出,则输出一个对应复杂对象成员的子元素,里面的元素值全为空。
 
这些特性是XStream所无法相比的。有关速度效率的问题,还没测试过。不过一般应用没有发现问题,除非你的xml几百M。