[Eclipse warning] "No grammar constraints (DTD or XML Schema) referenced in the document" in context.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- 下方加上-->
<!DOCTYPE xml>  
<Context>
<Resource name="jdbc/Project1" type="javax.sql.DataSource"
username="sa" password="xxxxxx" driverClassName="com.microsoft.sqlserver.jdbc.SQLServerDriver"
url="jdbc:sqlserver://localhost:1433;DatabaseName=Project1" maxActive="8"
maxIdle="4" maxWait="5000" />
</Context>