Code Resource: January 2010

1. Copy jdbc driver to Tomcat 5.X\common\lib
2. Romove all commons-dbcp-x.x.x,commons-pool-x.x and jdbc driver from application/WEB-INF/lib

3. Add Context and jndi parameters in server.xml file as below:

Tomcat 5.0.xx:
(the entity way) was the only way that worked.

[server.xml]:
<Service...>
<Engine...>
<Host...>
...
<Context crossContext="true" docBase="/opt/tomcat5/webapps/oracleTest" path="/oracleTest" reloadable="true">
<Resource name="jdbc/myoracle" auth="Container"
type="javax.sql.DataSource"/>
<ResourceParams name="jdbc/myoracle">
<parameter>
<name>factory</name>
<value>org.apache.commons.dbcp.BasicDataSourceFactory</value>
</parameter>
<parameter>
<name>driverClassName</name>
<value>oracle.jdbc.OracleDriver</value>
</parameter>
<parameter>
<name>url</name>
<value>jdbc:oracle:thin:@15.1.1.40:1521:dbastra</value>
</parameter>
<parameter>
<name>username</name>
<value>uuuuuu</value>
</parameter>
<parameter>
<name>password</name>
<value>xxxxxxxx</value>
</parameter>
<parameter>
<name>maxActive</name>
<value>20</value>
</parameter>
<parameter>
<name>maxIdle</name>
<value>10</value>
</parameter>
<parameter>
<name>maxWait</name>
<value>-1</value>
</parameter>
</ResourceParams>
<Resource name="jdbc/myoracle5" auth="Container"
type="javax.sql.DataSource" />
</Context>
</Host>
</Engine>
</Service>

Tomcat 5.5.xx:
(the attributes way) was the only way that worked.

[server.xml]:
<Service...>
<Engine...>
<Host...>
...
<Context path="/oracleTest" reloadable="true"
docBase="/opt/tomcat5/webapps/oracleTest">

<Logger className="org.apache.catalina.logger.SystemOutLogger"
verbosity="4" timestamp="true" />

<Resource name="jdbc/myoracle5" auth="Container"
type="javax.sql.DataSource" driverClassName="oracle.jdbc.OracleDriver"
url="jdbc:oracle:thin:@15.1.1.40:1521:dbastra" username="aradmin"
password="ar#admin#" maxActive="20" maxIdle="10" maxWait="-1" />

</Context>
</Host>
</Engine>
</Service>

for BOTH versions:

Here there are some points we should take a look:

<Context> in [server.xml] !!
"Please note that for tomcat 5, unlike tomcat 4.x, it is NOT recommended to place <Context> elements directly in the server.xml file. Instead, put them in the META-INF/context.xml directory of your WAR file or the conf directory as described above."
http://tomcat.apache.org/tomcat-5.5-doc/config/context.html

And if we cut the <Context>..</Context> body we described above from the server.xml and paste it into [META-INF/context.xml] or into [conf/Catalina/localhost/oracleTest.xml], it works...

<?xml version='1.0' encoding='utf-8'?>
<Context crossContext="true" docBase="/forge/oracleTest" path="/oracleTest" reloadable="true">
<Logger className="org.apache.catalina.logger.FileLogger"
prefix="localhost_DBTest_log." suffix=".txt" timestamp="true" />

<Resource ... (the one that applies to your version)>

</Context>

GlobalNamingResources:
"GlobalNamingResources element defines the global JNDI resources for the Server. These resources are listed in the server's global JNDI resource context. This context is distinct from the per-web-application JNDI contexts described in the JNDI Resources HOW-TO. The resources defined in this element are not visible in the per-web-application contexts unless you explicitly link them with <ResourceLink> elements."
http://tomcat.apache.org/tomcat-5.5-doc/config/globalresources.html
http://tomcat.apache.org/tomcat-5.5-doc/config/context.html#Resource%20Links

Article From http://forums.sun.com/thread.jspa?threadID=567630&start=15

dom4j提供了基于事件的模型来操作xml文档。利用该模型开发人员可以一部分、一部分的处理XML文档，而不需要将整个XML文档都加载到内存中。例如：假想你要处理一个非常大的XML文档，它可能是由数据库的某张数据表而来的。如下所示：
<ROWSET>
<ROW ID="1">
...
</ROW>
<ROW ID="2">
...
</ROW>
...
<ROW ID="N">
...
</ROW>
</ROWSET>
我们可以在某一时间只处理一个ROW节点，而不必立刻将文档的所有内容加载到内存中。dom4j提供一个基于事件的模型来实现它。我们可以注册一个事件处理器来处理一个或多个路径表达式。事件处理器会在注册路径的开始和结束时被调用执行。当注册路径的开始标签找到时执行事件处理器的 onStart()方法，当注册路径的结束标签被找到时执行事件处理器的onEnd()方法。

onStart()和onEnd()方法传递一个ElementPath实例参数，这个实例既为根据注册路径遍历xml文档时的当前节点（Element）。如果想对遍历的当前节点进行操作，可以在onEnd()方法中对当前节点调用detach()方法保存改。
下面是示例代码：

SAXReader reader = new SAXReader();
reader.addHandler( "/ROWSET/ROW",
new ElementHandler() {
public void onStart(ElementPath path) {
// do nothing here...
}
public void onEnd(ElementPath path) {
// process a ROW element
Element row = path.getCurrent();
Element rowSet = row.getParent();
Document document = row.getDocument();
...
// prune the tree
row.detach();
}
}
);

Document document = reader.read(url);
上面的办法解决了读的问题可是写的问题还没有解决。我命由我不由天（吹牛皮），畅游dom4j的doc文档找到如下几个方法
startDocument()
writeOpen();
writeClose();
endDocument()
动手一试，问题搞定，看来牛皮没白吹。下面是示例代码：

/**
* 数据写入xml文件
* @param filePath 目标xml文件的存放路径
* @return
*/
public boolean writeXML(String filePath){
XMLWriter out;
try {

/*
* 创建XMLWriter对象，设置XML编码，解决中文问题。
*/
OutputFormat outputFormat = OutputFormat.createPrettyPrint();
outputFormat.setEncoding("GBK");
out = new XMLWriter(new FileWriter(filePath),outputFormat);

out.startDocument();
Element rootElement = DocumentHelper.createElement("mans");
out.writeOpen(rootElement);

/*
* 向mans节点写入子节点
*/
for(int i=0 ; i<1000000 ; i++){
Element man = createManElement(new Long(i), "shuhang"+i);//用于创建节点的方法
out.write(man);
System.out.println(" the loop index is : " + i);
}

out.writeClose(rootElement);
out.endDocument();

out.close();
return true;
} catch (IOException e) {
e.printStackTrace();
return false;
} catch (SAXException e) {
e.printStackTrace();
return false;
}
}

新问题出现。对于读取数据的方法，在onEnd()方法中只是进行对Element的简单操作而已，若要对Element进行复杂的处理怎么办，如将Element节点的数据写入数据库，无法在onEnd()方法中加入过多的代码，因为无法通过编译。仔细想了一下dom4j的注册事件处理器应该用的是模板方法，通过钩子将用户的操作加入到模板中去。何不自己写一个事件处理器来完成我们自己的定制操作，代码如下：

public class ManElementHandler implements ElementHandler {
public String mdbName;

public ManElementHandler(){

}

public ManElementHandler(String mdbName){
this.mdbName = mdbName;
}

public boolean saveMan(Element element, String mdbName){
return true;
}

public void onEnd(ElementPath arg0) {
Element row = arg0.getCurrent();
Element rowSet = row.getParent();
Document document = row.getDocument();
Element root = document.getRootElement();
Iterator it = root.elementIterator();
while(it.hasNext()){
Element element = (Element)it.next();
System.out.println(" id : " + element.elementText("id") + " name : " + element.elementText("name"));
saveMan(element, this.mdbName);
}
row.detach();
}
public void onStart(ElementPath path) {

}
}

下面给出完整的实例代码。该实例首先创建一个xml文档，然后读取xml文档中的数据并将数据写入Access数据库中。测试时使用的文件大小为125M未发生内存溢出。

//*****************************************************************************************************************
package com;
import java.sql.Connection;
import java.sql.DriverManager;
/**
* 获取Access数据库的连接
* @author 佛山无影脚
* @version 1.0
* Jul 7, 2008 4:35:49 PM
*/
public class AccessMDBUtil {
public static Connection connectMdb(String mdbName) {
if(mdbName == null mdbName.equals("")){
return null;
}
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
String dburl ="jdbc:odbc:driver={Microsoft Access Driver (*.mdb)};DBQ="+mdbName;
Connection conn=DriverManager.getConnection(dburl);
return conn;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}
//*******************************************************************************************************************
//*******************************************************************************************************************
package com;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Iterator;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.ElementHandler;
import org.dom4j.ElementPath;
/**
* 定制的事件处理器
* @author 佛山无影脚
* @version 1.0
* Jul 7, 2008 4:35:49 PM
*/
public class ManElementHandler implements ElementHandler {
public String mdbName;//数据库名称含路径

public ManElementHandler(){

}

public ManElementHandler(String mdbName){
this.mdbName = mdbName;
}

/**
*将Element节点数据保存到数据库
*@param element 遍历XML文档时的当前节点
*@param mdbName 数据库名称含路径
*@return
*/
public boolean saveMan(Element element, String mdbName){
System.out.println(" the method saveMan in ManElementHandler is execute!");
Statement stmt = null;
ResultSet rs = null;
Connection conn = null;
try {
conn= AccessMDBUtil.connectMdb(mdbName);
stmt=conn.createStatement();
String sql = "insert into mans(id,name) values(" + element.elementText("id") + ",'" + element.elementText("name") + "')";
stmt.executeUpdate(sql);

} catch (Exception e) {
e.printStackTrace();
return false;
} finally {
if(rs != null) {
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(conn != null) {
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}

return true;
}

public void onEnd(ElementPath arg0) {
Element row = arg0.getCurrent();
Element rowSet = row.getParent();
Document document = row.getDocument();
Element root = document.getRootElement();
Iterator it = root.elementIterator();
while(it.hasNext()){
Element element = (Element)it.next();
System.out.println(" id : " + element.elementText("id") + " name : " + element.elementText("name"));
saveMan(element, this.mdbName);
}
row.detach();
}
public void onStart(ElementPath path) {

}
}
//*************************************************************************************************************************
//*************************************************************************************************************************
package com;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
/**
* 测试
* @author 佛山无影脚
* @version 1.0
* Jul 7, 2008 4:35:49 PM
*/
public class ManTest {
/**
* 创建man节点
* <man><id>1</id><name>佛山无影脚</name></man>
* @param id
* @param name
* @return
*/
public Element createManElement(Long id,String name){
Element manElement = DocumentHelper.createElement("man");
manElement.addElement("id").addText(id.toString());
manElement.addElement("name").addText(name);
return manElement;
}

/**
* 数据写入xml文件
* @param filePath 目标xml文件的存放路径
* @return
*/
public boolean writeXML(String filePath){
XMLWriter out;
try {

/*
* 创建XMLWriter对象，设置XML编码，解决中文问题。
*/
OutputFormat outputFormat = OutputFormat.createPrettyPrint();
outputFormat.setEncoding("GBK");
out = new XMLWriter(new FileWriter(filePath),outputFormat);

out.startDocument();
Element rootElement = DocumentHelper.createElement("mans");
out.writeOpen(rootElement);

/*
* 向mans节点写入子节点
*/
for(int i=0 ; i<1000000 ; i++){
Element man = this.createManElement(new Long(i), "shuhang"+i);
out.write(man);
System.out.println(" the loop index is : " + i);
}

out.writeClose(rootElement);
out.endDocument();

out.close();
return true;
} catch (IOException e) {
e.printStackTrace();
return false;
} catch (SAXException e) {
e.printStackTrace();
return false;
}
}

/**
* 从xml文件中读取数据，并将数据写入Access数据
* @param filePath xml文件的存放路径
* @return
*/
public boolean readXML(String filePath){

ManElementHandler manElementHandler = new ManElementHandler("F:\\dom4j\\xmlTest.mdb");
SAXReader reader = new SAXReader();
reader.addHandler( "/mans/man", manElementHandler);
Document document = null;
try {
File file = new File(filePath);
document = reader.read(file);
} catch (DocumentException e) {
e.printStackTrace();
return false;
}
return true;
}

public static void main(String[] args){
XMLReader reader = null;
long startTime = System.currentTimeMillis();
ManTest mantest = new ManTest();

mantest.writeXML("f:\\dom4j\\mans.xml");
mantest.readXML("f:\\dom4j\\mans.xml");

long endTime = System.currentTimeMillis();
System.out.println(" is end! the millis is : " + (endTime - startTime));

}
}
//*************************************************************************************************************************

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/shuhang1106/archive/2008/07/09/2627581.aspx

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