Tomcat 8（八）Tomcat解析server.xml的工具—Digester

Tomcat是利用Digester解析server.xml。Digester是Apache下的開源項目

Digester官網：http://commons.apache.org/proper/commons-digester/

使用Digester，需要依賴一些jar包。Digester依賴的jar包可以從網上下載，也可以使用Tomcat提供的jar包

方案一：從網上下載jar包

commons-beanutils.jar

commons-digester.jar

commons-logging.jar

commons-collections.jar(下載commons-collections-3。commons-collections-4將commons-collections的package命名由org.apache.commons.collections改爲org.apache.commons.collections4，而Digester內部仍按org.apache.commons.collections使用的)

方案二：使用Tomcat目錄下的jar包

tomcat-juli.jar($CATALINA_HOME\bin)

tomcat-util.jar($CATALINA_HOME\lib)

tomcat-util-scan.jar($CATALINA_HOME\lib)

本文采用方案一

下面來看看Digester如何解析School.xml

<?xml version='1.0' encoding='utf-8'?>
<School name="CSDN">
	<Grade name="1">
		<Class name="1" number="31"/>
		<Class name="2" number="32"/>
	</Grade>
	<Grade name="2">
		<Class name="1" number="41"/>
		<Class name="2" number="42"/>
	</Grade>
</School>

School是School.xml的最頂層節點，School節點下包含Grade節點，Grade節點下包含Class節點。(學校下有兩個年級，每個年級下有兩個班級，班級下的number表示人數)

首先要創建與School.xml中各個節點對應的實體類School.java、Grade.java、Class.java(這些類都放在digester包下)

School.java

package digester;

public class School {
	private String name;
	private Grade grades[] = new Grade[0];
	private final Object servicesLock = new Object();
	
	public void addGrade(Grade g){
		synchronized (servicesLock) {
			Grade results[] = new Grade[grades.length + 1];
            System.arraycopy(grades, 0, results, 0, grades.length);
            results[grades.length] = g;
            grades = results;
        }
	}
	
	public Grade[] getGrades() {
		return grades;
	}
	
	public String getName() {
		return name;
	}

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

}

School裏的Grade數組用來存放School包含的Grade。調用School. addGrade(Grade g)，可以往Grade數組添加Grade

Grade.java

package digester;

public class Grade {
	private String name;
	private Class classes[] = new Class[0];
	private final Object servicesLock = new Object();
	
	public void addClass(Class c){
		synchronized (servicesLock) {
			Class results[] = new Class[classes.length + 1];
            System.arraycopy(classes, 0, results, 0, classes.length);
            results[classes.length] = c;
            classes = results;
        }
	}
	
	public Class[] getClasses() {
		return classes;
	}
	
	public String getName() {
		return name;
	}
	
	public void setName(String name) {
		this.name = name;
	}
	
}

Class.java

package digester;

public class Class {
	private String name;
	private int number;
	
	public String getName() {
		return name;
	}
	
	public void setName(String name) {
		this.name = name;
	}
	
	public int getNumber() {
		return number;
	}
	
	public void setNumber(int number) {
		this.number = number;
	}
	
}

然後創建測試類DigesterTest.java。DigesterTest.java的digester方法用來讀取School.xml、創建Digester並設置規則、解析School.xml；print方法用來打印School的信息

package digester;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

import org.apache.tomcat.util.digester.Digester;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

public class DigesterTest {
	private School school;
	
	public School getSchool() {
		return school;
	}

	public void setSchool(School s) {
		this.school = s;
	}

	public void digester() throws IOException, SAXException{
		//讀取School.xml
		File file = new File("D:\\School.xml");
		InputStream inputStream = new FileInputStream(file);
		InputSource inputSource = new InputSource(file.toURI().toURL().toString());;
		inputSource.setByteStream(inputStream);
		//創建Digester
	    Digester digester = new Digester();
	    //是否需要用DTD驗證XML文檔的合法性
	    digester.setValidating(false);
	    //將當前對象放到對象堆的最頂層
	    digester.push(this);
	    
	    /* 下面開始爲Digester創建匹配規則
	     * 在Digester內School、School/Grade、School/Grade/Class
	     * 分別對應School.xml的School、Grade、Class節點
	     */
	    
	    //爲School創建規則
	    /*
	     * Digester.addObjectCreate(String pattern, String className, String attributeName)
	     * pattern--匹配的節點
	     * className--該節點對應的默認實體類
	     * attributeName--如果該節點有className屬性,用className的值替換默認實體類
	     * Digester匹配到School節點，如果School節點沒有className屬性，將創建digester.School對象；如果School節點有className屬性，將創建指定的(className屬性的值)對象
	    */
	    digester.addObjectCreate("School",
                "digester.School",
                "className");
	    //將指定節點的屬性映射到對象，即將School節點的name的屬性映射到School.java
	    digester.addSetProperties("School");
	    /*
	     * Digester.addSetNext(String pattern, String methodName, String paramType)
	     * pattern--匹配的節點
	     * methodName--調用父節點的方法
	     * paramType--父節點的方法接收的參數類型
	     * Digester匹配到School節點，將調用DigesterTest(School的父節點)的setSchool方法，參數爲School對象
	     */
	    digester.addSetNext("School",
           "setSchool",
           "digester.School");
	    
	    //爲School/Grade創建規則
	    digester.addObjectCreate("School/Grade",
                "digester.Grade",
                "className");
	    digester.addSetProperties("School/Grade");
	    //Grade的父節點爲School
	    digester.addSetNext("School/Grade",
           "addGrade",
           "digester.Grade");
	    
	    //爲School/Grade/Class創建規則
	    digester.addObjectCreate("School/Grade/Class",
                "digester.Class",
                "className");
	    digester.addSetProperties("School/Grade/Class");
	    digester.addSetNext("School/Grade/Class",
           "addClass",
           "digester.Class");
	    digester.parse(inputSource);
	}
	
	//打印School信息
	public void print(School s){
		if(s!=null){
			System.out.println(s.getName() + "有" + s.getGrades().length + "個年級");
			for(int i=0;i<s.getGrades().length;i++){
				if(s.getGrades()[i] !=null){
					Grade g = s.getGrades()[i];
					System.out.println(g.getName() + "年級 有 " + g.getClasses().length + "個班：");
					for(int j=0;j<g.getClasses().length;j++){
						if(g.getClasses()[j] !=null){
							Class c = g.getClasses()[j];
							System.out.println(c.getName() + "班有" + c.getNumber() + "人");
						}
					}
				}
			}
		}
	}
	
	public static void main(String[] args) throws IOException, SAXException {
		DigesterTest digesterTest = new DigesterTest();
		digesterTest.digester();
		digesterTest.print(digesterTest.school);
	}
}

DigesterTest的輸出：

CSDN有2個年級
1年級 有 2個班：
1班有31人
2班有32人
2年級 有 2個班：
1班有41人
2班有42人

Tomcat解析server.xml是在Catalina的load方法內進行的。load方法可以劃分成三步：

1. 創建Digester並設置規則

load方法內通過Digester digester = createStartDigester()創建Digester 並設置規則。createStartDigester也是Catalina內的方法

createStartDigester方法的內容(爲了簡介，每種創建規則的方式各列一個)

protected Digester createStartDigester() {
        Digester digester = new Digester();
        digester.setValidating(false);
        digester.setRulesValidation(true);
        HashMap<Class<?>, List<String>> fakeAttributes = new HashMap<>();
        ArrayList<String> attrs = new ArrayList<>();
        attrs.add("className");
        fakeAttributes.put(Object.class, attrs);
        digester.setFakeAttributes(fakeAttributes);
        digester.setUseContextClassLoader(true);

        digester.addObjectCreate("Server",
                                 "org.apache.catalina.core.StandardServer",
                                 "className");
        digester.addSetProperties("Server");
        //父節點爲Catalina
		digester.addSetNext("Server",
                            "setServer",
                            "org.apache.catalina.Server");

        digester.addObjectCreate("Server/Service",
                                 "org.apache.catalina.core.StandardService",
                                 "className");
        digester.addSetProperties("Server/Service");
		//父節點爲Server
        digester.addSetNext("Server/Service",
                            "addService",
                            "org.apache.catalina.Service");
		//爲Connector節點創建規則
        digester.addRule("Server/Service/Connector",
                         new ConnectorCreateRule());

        /*
		 * 如果某個節點包含的規則比較多，可以爲該節點創建一個規則類
		 * 執行digester.addRuleSet(new EngineRuleSet("Server/Service/")) 
		 * 可以將EngineRuleSet內包含的規則，添加到當前digester中
		 */
        digester.addRuleSet(new EngineRuleSet("Server/Service/"));
		//爲Cluster節點創建規則
        addClusterRuleSet(digester, "Server/Service/Engine/Host/Cluster/");
    }

2. 讀取server.xml文件

InputSource inputSource = null;
        InputStream inputStream = null;
        File file = null;
        try {
            file = configFile();
            inputStream = new FileInputStream(file);
            inputSource = new InputSource(file.toURI().toURL().toString());
        } catch (Exception e) {
            if (log.isDebugEnabled()) {
                log.debug(sm.getString("catalina.configFail", file), e);
            }
        }

3. 利用Digester解析xml文件

try {
            inputSource.setByteStream(inputStream);
            digester.push(this);
            digester.parse(inputSource);
        } catch (SAXParseException spe) {
            log.warn("Catalina.start using " + getConfigFile() + ": " +
                    spe.getMessage());
            return;
        } catch (Exception e) {
            log.warn("Catalina.start using " + getConfigFile() + ": " , e);
            return;
        } finally {
            try {
                inputStream.close();
            } catch (IOException e) {
                // Ignore
            }
        }

參考文章：

http://blog.csdn.net/caihaijiang/article/details/5944955

http://www.cnblogs.com/bjzhanghao/archive/2005/03/25/125747.html

Tomcat 8（八）Tomcat解析server.xml的工具—Digester

PowerShell如何使用自定義公共函數

C#中使用log4net

WCF ServiceHost的實例方式及ServiceHost實例的併發方式

WCF託管在IIS、Windows Services下的性能對比

Tomcat 8（八）Tomcat解析server.xml的工具—Digester

Mac下配置sublime實現LaTeX

https://yachay.unat.edu.pe/blog/index.php?comment_area=format_blog&comment_component=blog&comment_co

linux以太網驅動總結