在tomcat->conf->catalina->localhost下建一个与你工程名相同的xml文件
<?xml version='1.0' encoding='utf-8'?>
<Context displayName="Welcome to Tomcat" docBase="工程名" path="" workDir="work\Catalina\localhost\_">
<Resource name="jdbc/数据库名" auth="Container" type="javax.sql.DataSource"/> 
<ResourceParams name="jdbc/数据库名">
<parameter>
          <name>factory</name>
          <value>org.apache.commons.dbcp.BasicDataSourceFactory</value>
        </parameter>
        <parameter>
          <name>maxActive</name>
          <value>500</value>
        </parameter>
        <parameter>
          <name>maxIdle</name>
          <value>500</value>
        </parameter>
        <parameter>
          <name>maxWait</name>
          <value>1000</value>
        </parameter> 
   <parameter>
         <name>username</name>
         <value>sa</value>
        </parameter>
        <parameter>
         <name>password</name>
         <value>数据库密码</value>
        </parameter>
        <parameter>
           <name>driverClassName</name>
           <value>com.microsoft.jdbc.sqlserver.SQLServerDriver</value>
        </parameter>
        <parameter>
          <name>url</name>
          <value>jdbc:microsoft:sqlserver://localhost:1433;databasename=你的数据库名</value>
        </parameter>
</ResourceParams>
</Context>