1>. Properties：使用配置文件Properties，要求文件必须和.java在同一个package下，否则无法找到。配置文件如下：
driver=com.mysql.jdbc.Driver
url=jdbc\:mysql\://192.168.0.13\:3306/myweb
username=root
password=lovejack
构造器如下：
public class DbBean {
private Connection con = null;
private Properties props = new Properties();
public DbBean() {
try {
props.load(this.getClass().getResourceAsStream(
"dbconfig.properties"));
Class.forName(props.getProperty("driver"));
con = DriverManager.getConnection(props.getProperty("url"), props.getProperty("username"), props.getProperty("password"));
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
2>.ServletContext：配置局部xml文件，位于工程目录下WEB-INF文件夹内的web.xml，在其内增加字段：
<context-param>
<param-name>driver</param-name>
<param-value>com.mysql.jdbc.Driver</param-value>
</context-param>
<context-param>
<param-name>url</param-name>
<param-value>jdbc:mysql://192.168.0.13:3306/myweb</param-value>
</context-param>
<context-param>
<param-name>username</param-name>
<param-value>root</param-value>
</context-param>
<context-param>
<param-name>password</param-name>
<param-value>lovejack</param-value>
</context-param>
构造器：
public DbBean(ServletContext context) {
try {
Class.forName(context.getInitParameter("driver"));
con = DriverManager.getConnection(context.getInitParameter("url"), context.getInitParameter("username"), context.getInitParameter("password"));
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
3>.ServletConfig：全局xml文件，位于tomcat\conf \web.xml, 在<servlet> </servlet>增加字段如下：
<init-param>
<param-name>driver</param-name>
<param-value>com.mysql.jdbc.Driver</param-value>
</init-param>
<init-param>
<param-name>url</param-name>
<param-value>jdbc\:mysql\://192.168.0.13\:3306/myweb</param-value>
</init-param>
<init-param>
<param-name>username</param-name>
<param-value>root</param-value>
</init-param>
<init-param>
<param-name>password</param-name>
<param-value>lovejack</param-value>
</init-param>
构造器：
public void open(ServletConfig config) {
try {
Class.forName(config.getInitParameter("driver"));
con = DriverManager.getConnection(config.getInitParameter("url"), config.getInitParameter("username"), config.getInitParameter("password"));
}
catch (ClassNotFoundException e) {
e.printStackTrace();
}
catch (SQLException e) {
e.printStackTrace();
}
}