XML解析和生成之--pull(android内置)

Pull是Android内置的xml解析器。Pull解析器的运行方式与SAX 解析器相似。它提供了类似的事件，如：开始元素和结束元素事件，使用parser.next()可以进入下一个元素并触发相应事件。事件将作为数值代码被发送，因此可以使用一个switch对感兴趣的事件进行处理。当元素开始解析时，调用parser.nextText()方法可以获取下一个Text类型节点的值。

下面我们来写代码学习pull解析技术。

要解析的xml文件名为：target.xml，解析的内容如下：

<?xml version="1.0" encoding="UTF-8"?>
<persons>
    <person id="23">
        <name>liming</name>
        <age>30</age>
    </person>
    <person id="20">
        <name>lixiangmei</name>
        <age>25</age>
    </person>
</persons>

 同样，我们在android的工程下写代码测试，使用android的单元测试技术进行测试，当然测试类还要继承AndroidTestCase

在layout/res/AndroidManifest.xml文件下添加单元测试所需要的代码：

在AndroidManifest.xml文件的application节点下添加以下代码：

 

<uses-library android:name="android.test.runner" />

在AndroidManifest.xml文件的manifest节点下添加以下代码：

<instrumentation android:name="android.test.InstrumentationTestRunner" android:targetPackage="你的测试文件所在的包名" android:label="Tests for My App" />

 

public class Person {
    private Integer id;
    private String name;
    private Short age;
    public Person(){}//无参构造器

    public Person(Integer id, String name, Short age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Short getAge() {
        return age;
    }
    public void setAge(Short age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Person [age=" + age + ", id=" + id + ", name=" + name + "]";
    }
}

pull解析的核心类：PULLPersonService.java，里面包含两个方法，一个是生成xml文件的方法，一个事解析xml文件的方法。

/**
 * 采用Pull解析XML内容
 */
public class PULLPersonService {

    /**
     * 使用pull技术生成xml文件
     * @param persons
     * @param writer
     * @throws Throwable
     */
    public static void save(List<Person> persons, Writer writer) throws Throwable{
        XmlSerializer serializer = Xml.newSerializer();
        serializer.setOutput(writer);
        serializer.startDocument("UTF-8", true);

        serializer.startTag(null, "persons");
        for(Person person : persons){
            serializer.startTag(null, "person");
            serializer.attribute(null, "id", person.getId().toString());

            serializer.startTag(null, "name");
            serializer.text(person.getName());
            serializer.endTag(null, "name");

            serializer.startTag(null, "age");
            serializer.text(person.getAge().toString());
            serializer.endTag(null, "age");

            serializer.endTag(null, "person");
        }
        serializer.endTag(null, "persons");
        serializer.endDocument();
        writer.flush();
        writer.close();
    }

    /**
     * 使用pull技术解析xml
     * @param inStream
     * @return
     * @throws Throwable
     */
    public static List<Person> getPersons(InputStream inStream) throws Throwable{
        List<Person> persons = null;
        Person person = null;
        XmlPullParser parser = Xml.newPullParser();
        parser.setInput(inStream, "UTF-8");
        int eventType = parser.getEventType();//产生第一个事件
        while(eventType!=XmlPullParser.END_DOCUMENT){//只要不是文档结束事件
            switch (eventType) {
            case XmlPullParser.START_DOCUMENT:
                persons = new ArrayList<Person>();
                break;

            case XmlPullParser.START_TAG:
                String name = parser.getName();//获取解析器当前指向的元素的名称
                if("person".equals(name)){
                    person = new Person();
                    person.setId(new Integer(parser.getAttributeValue(0)));
                }
                if(person!=null){
                    if("name".equals(name)){
                        person.setName(parser.nextText());//获取解析器当前指向元素的下一个文本节点的值
                    }
                    if("age".equals(name)){
                        person.setAge(new Short(parser.nextText()));
                    }
                }
                break;
            case XmlPullParser.END_TAG:
                if("person".equals(parser.getName())){
                    persons.add(person);
                    person = null;
                }
                break;
            }
            eventType = parser.next();
        }
        return persons;
    }
}

public class PersonServiceTest extends AndroidTestCase {
    private static final String TAG = "PersonServiceTest";

    public void testPullGetPersons() throws Throwable{
        InputStream inStream = getClass().getClassLoader().getResourceAsStream("target.xml");
        List<Person> persons = PULLPersonService.getPersons(inStream);
        for(Person person : persons){
            Log.i(TAG, person.toString());
        }
    }

    public void testSave() throws Throwable{
        List<Person> persons = new ArrayList<Person>();
        persons.add(new Person(34, "lili", (short)12));
        persons.add(new Person(25, "mimi", (short)32));
        persons.add(new Person(33, "xixi", (short)40));
        StringWriter writer = new StringWriter();
        PULLPersonService.save(persons, writer);
        Log.i(TAG, writer.toString());
    }
}

public class PersonServiceTest extends AndroidTestCase {
	private static final String TAG = "PersonServiceTest";
	
	public void testPullGetPersons() throws Throwable{
		InputStream inStream = getClass().getClassLoader().getResourceAsStream("target.xml");
		List<Person> persons = PULLPersonService.getPersons(inStream);
		for(Person person : persons){
			Log.i(TAG, person.toString());
		}
	}
	
	public void testSave() throws Throwable{
		List<Person> persons = new ArrayList<Person>();
		persons.add(new Person(34, "lili", (short)12));
		persons.add(new Person(25, "mimi", (short)32));
		persons.add(new Person(33, "xixi", (short)40));
		StringWriter writer = new StringWriter();
		PULLPersonService.save(persons, writer);
		Log.i(TAG, writer.toString());
	}
}

用单元测试运行testPullGetPersons()方法，运行结果如下：

Person [age=30, id=23, name=liming]
Person [age=25, id=20, name=lixiangmei]

 用单元测试运行 testSave()方法，运行结果如下：

<?xml version='1.0' encoding='UTF-8' standalone='yes' ?>
<persons>
    <person id="34">
        <name>lili</name>
        <age>12</age>
    </person>
    <person id="25">
        <name>mimi</name>
        <age>32</age>
    </person>
    <person id="33">
        <name>xixi</name>
        <age>40</age>
    </person>
</persons>

 到此完成了用pull技术完成xml的解析，和生成xml文件。 

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