Digester

1. 介绍

这是一个apache 用于解析XML的工具类，这里依赖到的包有以下几个

• commons-digester3-3.2.jar
• cglib-2.2.2.jar
• asm-3.3.1.jar
• commons-beanutils-1.8.3.jar
• commons-logging-1.1.1.jar

2.案例说明

下面就用一个实际的几个类来说明他的用法

测试类

import java.io.File;
import java.io.IOException;

import org.apache.commons.digester3.Digester;
import org.xml.sax.SAXException;

import com.io.test.apache.digester.model.DigesterRule;
import com.io.test.apache.digester.model.School;
import com.io.test.apache.digester.model.SchoolClass;

public class DigesterTest {

    public static void main(String[] args) {
        //创建一个Digester
        Digester d = new Digester();
        
        //添加规则组
        d.addRuleSet(new DigesterRule());
        try {
            //开始解析xml文件，这列就是按照上面所设的规则组合来决定如何解析这个xml
            School school = (School)d.parse(new File("./src/com/io/test/apache/digester/test.xml"));
            System.out.println(school.getName());
            
            for(SchoolClass sc : school.getSchoolClasses()){
                System.out.println(sc.getClassName());
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SAXException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

规则组-1

import org.apache.commons.digester3.CallMethodRule;
import org.apache.commons.digester3.Digester;
import org.apache.commons.digester3.ObjectCreateRule;
import org.apache.commons.digester3.Rule;
import org.apache.commons.digester3.RuleSetBase;
import org.apache.commons.digester3.SetNestedPropertiesRule;
import org.apache.commons.digester3.SetNextRule;

public class DigesterRule extends RuleSetBase {

    @Override
    public void addRuleInstances(Digester arg0) {
        //遇到shcool节点的时候，创建一个School对象
        arg0.addRule("school", new ObjectCreateRule(School.class));
        
        //遇到school/detail节点的时候，把子节点的内容存放在顶层对象(School)对象当中
        arg0.addRule("school/detail", createSetNestedPropertiesRule());
        
        //添加新的规则组，这里对应的是规则组-2
        arg0.addRuleSet(new ClassRule());
        
        //遇到school/classes/class节点的时候，执行addClass的时候方法，并且以上一个创建的对象作为参数传递，
        arg0.addRule("school/classes/class", new SetNextRule("addClass"));
    }

    /**
     * 在该指定路径下的所有节点，都会被设置到最顶端的对象当中
     * @return
     */
    public Rule createSetNestedPropertiesRule() {
        SetNestedPropertiesRule rule = new SetNestedPropertiesRule();
        rule.setAllowUnknownChildElements(true);
        return rule;
    }

    /**
     * 调用方法规则
     * 指定路径下的节点获取到的值，会通过调用指定方法，执行，默认参数为String
     * @param methodName
     * @param paramCount
     * @return
     */
    public Rule createCallMethodRule(String methodName, int paramCount) {
        return new CallMethodRule(methodName, paramCount);
    }
}

规则组-2

import org.apache.commons.digester3.Digester;
import org.apache.commons.digester3.ObjectCreateRule;
import org.apache.commons.digester3.RuleSetBase;
import org.apache.commons.digester3.SetNestedPropertiesRule;

public class ClassRule extends RuleSetBase {

    @Override
    public void addRuleInstances(Digester arg0) {
        //遇到school/classes/class节点的时候，创建一个schoolClass对象
        arg0.addRule("school/classes/class", new ObjectCreateRule(SchoolClass.class));
        
        //遇到school/classes/class节点的时候，把所有子节点的内容存放在顶层对象(schoolClass)的属性当中
        arg0.addRule("school/classes/class", new SetNestedPropertiesRule());

    }

}

其它模型类

学校模型

public class School {

    private String name;
    private String address;
    private List<SchoolClass> schoolClasses;

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getName() {
        return name;
    }

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

    public void addClass(SchoolClass schoolClass){
        if(schoolClasses == null){
            schoolClasses = new ArrayList<SchoolClass>();
        }
        this.schoolClasses.add(schoolClass);
    }
    
    public List<SchoolClass> getSchoolClasses() {
        return schoolClasses;
    }
}

班级模型

public class SchoolClass {

    private String className;

    private List<Student> students;

    public SchoolClass() {
        students = new ArrayList<Student>();
    }

    public String getClassName() {
        return className;
    }

    public void setClassName(String className) {
        this.className = className;
    }

    public List<Student> getStudents() {
        return students;
    }

    public void setStudents(List<Student> students) {
        this.students = students;
    }
}

XML文件

<?xml version="1.0" encoding="utf-8" ?>
<school>
    <detail>
        <name>学校-1</name>
        <address>北京</address>
    </detail>
    <classes>
        <class>
            <className>class-1</className>
        </class>
    </classes>
    
    
</school>