解析xml文件并且输出（SAX解析器）

本文解析三个xml文件，难度依次增加

文件1：p1.xml

<?xml version="1.0" encoding="UTF-8" ?>
<persons>
    <person>
      <name>张三</name>
      <age>22</age>
   </person>
</persons>

文件2：p2.xml

<?xml version="1.0" encoding="UTF-8" ?>
<persons>
    <person>
      <name>张三</name>
      <age>33</age>
   </person>
   <person>
      <name>李四</name>
      <age>44</age>
   </person>
</persons>

文件3：p3.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app>
    <servlet>
        <servlet-name>login</servlet-name>
        <servlet-class>cs.cwnu.servlet.LoginServlet
        </servlet-class>
    </servlet>
    <servlet>
        <servlet-name>reg</servlet-name>
        <servlet-class>cs.cwnu.servlet.RegisterServlet
        </servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>login</servlet-name>
        <url-pattern>/login</url-pattern>
        <url-pattern>/g</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>reg</servlet-name>
        <url-pattern>/reg</url-pattern>
    </servlet-mapping>
</web-app>

首先解析文件1

public class XmlTest {

    public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException {
        //SAX解析
        //1、获取解析工厂
        SAXParserFactory factory=SAXParserFactory.newInstance();
        //2、从解析工厂获取解析器
        SAXParser parse =factory.newSAXParser();
        //3、编写处理器
        //4、加载文档 Document 注册处理器
        PHandler handler=new PHandler();
        //5、解析
        parse.parse(Thread.currentThread().getContextClassLoader()
        .getResourceAsStream("cs/cwnu/test/p1.xml")
        ,handler);

    }

}
class PHandler extends DefaultHandler{
    @Override
    public void startDocument() throws SAXException {
        System.out.println("----解析文档开始----");
    }
    
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        System.out.println(qName+"元素解析开始");
    }
    
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        String contents = new String(ch,start,length).trim();
        if(contents.length()>0) {
            System.out.println("内容为"+contents);            
        }else {
            System.out.println("内容为空");        
        }
    }
    
    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        System.out.println(qName+"元素解析结束");
    }
    @Override
    public void endDocument() throws SAXException {
        System.out.println("----解析文档结束----");
    }
}
结果展示

----解析文档开始----
persons元素解析开始
内容为空
person元素解析开始
内容为空
name元素解析开始
内容为张三
name元素解析结束
内容为空
age元素解析开始
内容为22
age元素解析结束
内容为空
person元素解析结束
内容为空
内容为空
persons元素解析结束
----解析文档结束----

其次解析文件2

public class XmlTest02 {

    public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException {
        //SAX解析
        //1、获取解析工厂
        SAXParserFactory factory=SAXParserFactory.newInstance();
        //2、从解析工厂获取解析器
        SAXParser parse =factory.newSAXParser();
        //3、编写处理器
        //4、加载文档 Document 注册处理器
        PersonHandler handler=new PersonHandler();
        //5、解析
        parse.parse(Thread.currentThread().getContextClassLoader()
        .getResourceAsStream("cs/cwnu/test/p2.xml")
        ,handler);
        
        //获取数据
        List<Person> persons = handler.getPersons();
        for(Person p:persons) {
            System.out.println(p.getName()+"-->"+p.getAge());
        }
    }

}
class PersonHandler extends DefaultHandler{
    private List<Person> persons ;
    private Person person ;
    private String tag; //存储操作标签
    @Override
    public void startDocument() throws SAXException {
        persons = new ArrayList<Person>();
    }
    
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        if(null!=qName) {
            tag = qName; //存储标签名
            if(tag.equals("person")) {
                person = new Person();
            }
        }
    }
    
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        String contents = new String(ch,start,length).trim();
        if(null!=tag) { //处理了空
            if(tag.equals("name")) {
                person.setName(contents);
            }else if(tag.equals("age")) {
                if(contents.length()>0) {
                    person.setAge(Integer.valueOf(contents));
                }            
            }
        }
    }
    
    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if(null!=qName) { 
            if(qName.equals("person")) {
                persons.add(person);
            }
        }
        tag = null; //tag丢弃了
    }
    @Override
    public void endDocument() throws SAXException {
    }

    public List<Person> getPersons() {
        return persons;
    }
}
结果为：

张三-->33
李四-->44

最后解析文件3：p3.xml

用户访问的网址不同，会访问不同的Servlet

比如：访问“/login或/g”,用户会跳转到LoginServlet

访问“/reg”,用户会跳转到RegisterServlet

具体代码如下：

创建Entity类用来存放<Servlet>元素的内容

package cs.cwnu.servlet;

//<servlet>
//<servlet-name>login</servlet-name>
//<servlet-class>com.sxt.server.basic.servlet.LoginServlet
//</servlet-class>
//</servlet>

public class Entity {
    private String name;
    private String clz;
    public Entity(){
        
    }
    /**
     * @param name
     * @param clz
     */
    public Entity(String name, String clz) {
        super();
        this.name = name;
        this.clz = clz;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getClz() {
        return clz;
    }
    public void setClz(String clz) {
        this.clz = clz;
    }
    
}

创建Mapping类来存放<ServletMapping>元素的内容

package cs.cwnu.servlet;

import java.util.HashSet;
import java.util.Set;
//<servlet-mapping>
//<servlet-name>login</servlet-name>
//<url-pattern>/login</url-pattern>
//<url-pattern>/g</url-pattern>
//</servlet-mapping>
public class Mapping {
    private String name;
    private Set<String> patterns;
    /**
     * @param name
     * @param patterns
     */
    public Mapping() {
        patterns = new HashSet<String>();
    }
    public Mapping(String name, Set<String> patterns) {
        super();
        this.name = name;
        this.patterns = patterns;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Set<String> getPatterns() {
        return patterns;
    }
    public void setPatterns(Set<String> patterns) {
        this.patterns = patterns;
    }
    public void addPattern(String pattern){
        this.patterns.add(pattern);
    }
}

创建Servlet接口

package cs.cwnu.servlet;

public interface Servlet {
    void service();
}

创建LoginServlet实现Servlet类

package cs.cwnu.servlet;

public class LoginServlet implements Servlet {

    @Override
    public void service() {
        System.out.println("LoginServlet");
    }

}

创建RegisterServlet实现Servlet类

package cs.cwnu.servlet;

public class RegisterServlet implements Servlet {

    @Override
    public void service() {
        System.out.println("RegisterServlet");
    }

}

创建WebContext类，功能是用户输入url通过匹配<servlet-mapping>中的<url-pattern>的值，找到同级<servlet-name>的值，再找到与<servlet>中<servlet-name>值相同且同级的<servlet-class>的值，即找到Servlet类

package cs.cwnu.servlet;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class WebContext {
    private List<Entity> entitys=null;
    private List<Mapping> mappings=null;
    //key:servlet-name,value:servlet-class
    private Map<String,String> entityMap = new HashMap<String,String>();
    //key:url-pattern,value:servlet-name
    private Map<String,String> mappingMap = new HashMap<String,String>();
    
    /**
     * @param entitys
     * @param mappings
     */
    public WebContext(List<Entity> entitys, List<Mapping> mappings) {
        super();
        this.entitys = entitys;
        this.mappings = mappings;
        for (Entity entity : entitys) {
            entityMap.put(entity.getName(), entity.getClz());
        }
        for (Mapping mapping : mappings) {
            for(String pattern:mapping.getPatterns()){
                mappingMap.put(pattern, mapping.getName());
            }
        }
    }
    public String getClz(String pattern){
        String name = mappingMap.get(pattern);
        String clas = entityMap.get(name);
        return clas;
    }
}

测试代码：

package cs.cwnu.servlet;

import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class XmlTest01 {

    public static void main(String[] args) throws Exception{
        // SAX解析
        // 1、获取解析工厂
        SAXParserFactory factory = SAXParserFactory.newInstance();
        // 2、从解析工厂获取解析器
        SAXParser parse = factory.newSAXParser();
        // 3、编写处理器
        // 4、加载文档 Document 注册处理器
        WebHandler handler = new WebHandler();
        // 5、解析
        parse.parse(Thread.currentThread().getContextClassLoader().getResourceAsStream("cs/cwnu/servlet/web.xml"), handler);
        List<Entity> entitys = handler.getEntitys();
        List<Mapping> mappings = handler.getMappings();
        WebContext wb = new WebContext(entitys, mappings);
        
        //假设登录
        //String name = wb.getClz("/login");输出LoginServlet
        String name = wb.getClz("/g");
        //String name = wb.getClz("/reg");输出RegisterServlet
        Class clazz = Class.forName(name);
        Servlet servlet = (Servlet)clazz.getConstructor().newInstance();
        servlet.service();
    }

}

class WebHandler extends DefaultHandler {
    private List<Entity> entitys;
    private List<Mapping> mappings;
    private Entity entity;
    private Mapping mapping;
    private String tag;
    private boolean isMapping = false;

    @Override
    public void startDocument() throws SAXException {
        entitys = new ArrayList<Entity>();
        mappings = new ArrayList<Mapping>();
    }

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        if (null != qName) {
            tag = qName;
            if (tag.equals("servlet")) {
                entity = new Entity();
                isMapping = false;
            } else if (tag.equals("servlet-mapping")) {
                mapping = new Mapping();
                isMapping = true;
            }
        }
    }

    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        String contents = new String(ch, start, length).trim();
        if (null != tag) {
            if (isMapping) {
                if (tag.equals("servlet-name")) {
                    mapping.setName(contents);
                } else if (tag.equals("url-pattern")) {
                    mapping.addPattern(contents);
                }
            } else {
                if (tag.equals("servlet-name")) {
                    entity.setName(contents);
                } else if (tag.equals("servlet-class")) {
                    entity.setClz(contents);
                }
            }

        }

    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if (null != qName) {
            if (qName.equals("servlet")) {
                entitys.add(entity);
            } else if (qName.equals("servlet-mapping")) {
                mappings.add(mapping);
            }

        }
        tag = null;

    }

    @Override
    public void endDocument() throws SAXException {
    }

    public List<Entity> getEntitys() {
        return entitys;
    }

    public List<Mapping> getMappings() {
        return mappings;
    }

}

测试结果：LoginServlet