被osworkflow的数据库配置（mysql）困住了
今天研究了一下osworkflow,想运行一下他的例子程序看看效果。结果在配置与数据库连接方面出了问题，郁闷至极。
我用的是mysql数据库，按照
http://www.opensymphony.com/osworkflow/1.3%20Running%20the%20Example%20App.html一步一步的配置。
我的配置文件具体如下：
1：在tomcat的conf目录下修改server.xml，增加以下内容
<Context path="/osworkflow_example" docBase="osworkflow-2.7.0-example"
debug= "99" reloadable="true" crossContext="true" verbosity="DEBUG">
<!-- debug level is set to paranoid, to know what is happening,
turn it off once you do not need it -->
<Logger className="org.apache.catalina.logger.FileLogger"
prefix="OSWorkflow." suffix=".log" timestamp="true"/>
<!--
put log4j.jar into:
TOMCAT_ROOT/webapp/osworkflow-2.7.0-example/WEB-INF/lib
if you want to use it for logging
-->
<Resource name="jdbc/DefaultDS"
auth="Container"
type="javax.sql.DataSource"/>
<ResourceParams name="jdbc/DefaultDS">
<parameter>
<name>factory</name>
<value>org.apache.commons.dbcp.BasicDataSourceFactory</value>
</parameter>
<!--
<parameter>
<name>factory</name>
<value>org.apache.catalina.users.MemoryUserDatabaseFactory</value>
</parameter>
-->
<!-- Maximum number of dB connections in pool. Make sure you
configure your mysqld max_connections large enough to handle
all of your db connections. Set to 0 for no limit.
-->
<parameter>
<name>maxActive</name>
<value>100</value>
</parameter>
<!-- Maximum number of idle dB connections to retain in pool.
Set to 0 for no limit.
-->
<parameter>
<name>maxIdle</name>
<value>30</value>
</parameter>
<!-- Maximum time to wait for a dB connection to become available
in ms, in this example 10 seconds. An Exception is thrown if
this timeout is exceeded. Set to -1 to wait indefinitely.
-->
<parameter>
<name>maxWait</name>
<value>10000</value>
</parameter>
<!-- MySQL dB username and password for dB connections -->
<parameter>
<name>username</name>
<value>root</value>
</parameter>
<parameter>
<name>password</name>
<value></value>
</parameter>
<!-- Class name for mm.mysql JDBC driver -->
<parameter>
<name>driverClassName</name>
<value>org.gjt.mm.mysql.Driver</value>
</parameter>
<!-- The JDBC connection url for connecting to your MySQL dB.
The autoReconnect=true argument to the url makes sure that the
mm.mysql JDBC Driver will automatically reconnect if mysqld closed the
connection. mysqld by default closes idle connections after 8 hours.
-->
<parameter>
<name>url</name>
<value>jdbc:mysql://localhost:3306/osworkflow?autoReconnect=true</value>
</parameter>
</ResourceParams>
</Context>
2：配置osworkflow.xml(在WEB-INF\classes目录下)，内容如下：
<osworkflow>
<persistence class="com.opensymphony.workflow.spi.jdbc.MySQLWorkflowStore">
<!-- For jdbc persistence, all are required. -->
<property key="datasource" value="jdbc/DefaultDS"/>
<property key="entry.sequence"
value="select count(*) + 1 from os_wfentry"/>
<property key="entry.table" value="OS_WFENTRY"/>
<property key="entry.id" value="ID"/>
<property key="entry.name" value="NAME"/>
<property key="entry.state" value="STATE"/>
<!--
<property key="step.sequence" value="select sum(c1) from
(select 1 tb, count(*) c1 from os_currentstep
union select 2 tb, count(*) c1 from os_historystep)"/>
-->
<property key="step.sequence" value="select sum(c1) + 1 from (select 1 as
tb, count(*) as c1 from os_currentstep union select 2 as tb, count(*) as c1
from os_historystep) as TabelaFinal" />
<property key="step.sequence.increment" value="INSERT INTO OS_STEPIDS (ID) values (null)"/>
<property key="step.sequence.retrieve" value="SELECT max(ID) FROM OS_STEPIDS"/>
<property key="history.table" value="OS_HISTORYSTEP"/>
<property key="current.table" value="OS_CURRENTSTEP"/>
<property key="historyPrev.table" value="OS_HISTORYSTEP_PREV"/>
<property key="currentPrev.table" value="OS_CURRENTSTEP_PREV"/>
<property key="step.id" value="ID"/>
<property key="step.entryId" value="ENTRY_ID"/>
<property key="step.stepId" value="STEP_ID"/>
<property key="step.actionId" value="ACTION_ID"/>
<property key="step.owner" value="OWNER"/>
<property key="step.caller" value="CALLER"/>
<property key="step.startDate" value="START_DATE"/>
<property key="step.finishDate" value="FINISH_DATE"/>
<property key="step.dueDate" value="DUE_DATE"/>
<property key="step.status" value="STATUS"/>
<property key="step.previousId" value="PREVIOUS_ID"/>
</persistence>
</osworkflow>
3：增加propertyset.xml（在WEB-INF\classes目录下），内容如下：
<propertysets>
<propertyset name="jdbc" class="com.opensymphony.module.propertyset.database.JDBCPropertySet">
<arg name="datasource" value="jdbc/DefaultDS"/>
<arg name="table.name" value="OS_PROPERTYENTRY"/>
<arg name="col.globalKey" value="GLOBAL_KEY"/>
<arg name="col.itemKey" value="99vEM_KEY"/>
<arg name="col.itemType" value="99vEM_TYPE"/>
<arg name="col.string" value="STRING_VALUE"/>
<arg name="col.date" value="DATE_VALUE"/>
<arg name="col.data" value="DATA_VALUE"/>
<arg name="col.float" value="FLOAT_VALUE"/>
<arg name="col.number" value="NUMBER_VALUE"/>
</propertyset>
</propertysets>
4：修改web.xml,内容如下：
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd";>
<web-app>
<display-name>OSWorkflow Example App</display-name>
<welcome-file-list>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<resource-ref>
<description>OSWorkflow Example App</description>
<res-ref-name>jdbc/DefaultDS</res-ref-name>
<res-ref-type>javax.sql.DataSource</res-ref-type>
<res-auth>Container</res-auth>
</resource-ref>
</web-app>
5：将jboss-j2ee.jar拷贝到tomcat_home\common\endorsed目录下
6：将驱动程序拷贝到tomcat_home\common\lib目录下
7:启动tomcat但是报以下错误
严重: Parse error in application web.xml
java.lang.NullPointerException