peer-topeer Networks phần 3 ppt

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Better Development Environment 45

It is useful and more convenient in the learning and testing process. I recom￾mendyou to enable the invoker servlet if you are not familiar with Tomcat. You

can enable this function by modifying the web.xml under the conf path.

Steps to enable the invoker servlet are as follows:

1. Locate the following two blocks in the web.xml file in the conf directory.

<!

<servlet>

<servlet-name>invoker</servlet-name>

<servlet-class>

org.apache.catalina.servlets.InvokerServlet

</servlet-class>

<init-param>

<param-name>debug</param-name>

<param-value>0</param-value>

</init-param>

<load-on-startup>2</load-on-startup>

</servlet>

>

<!−

<servlet-mapping>

<servlet-name>invoker</servlet-name>

<url-pattern>/servlet/*</url-pattern>

</servlet-mapping>

>

2. Remove the first line and last line of the above two blocks (i.e., <! and

>).

3. Save the web.xml file. You can turn off this function by adding back the first

and last line to the blocks.

4. Create classes path under the C:\Tomcat 5.5\webapps\ROOT\WEB-INF.

5. Copy the simple.class of this book to the following path:

C:\Tomcat 5.5\webapps\ROOT\WEB-INF\classes

6. Start a web browser.

7. Type http://localhost:8080/servlet/simple as the URL. The browser will display

the screen as illustrated in Fig. 5.15.

Figure 5.15. Screen of the simple servlet

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46 5. Web Server and Related Technologies

5.5.4 Deployment of Servlets

It will be better to put the source files and compiled files (i.e., the class files) in

different directories when you have a lot of programs in your application. If you

are using an IDE tool (such as Jbuilder), then the IDE will take care of compilation

and put the class file in the right directory. However, if you do not have an IDE on

your computer, you can use the following command:

javac –d directory of the class name.java

For example, the following command will compile a simple.java program

and store the simple.class file in the c:\Tomcat 5.5\webapps\ROOT\WEB￾INF\classes.

e.g.,javac –d c:\Tomcat 5.5\webapps\ROOT\WEB-INF\classes simple.java

You can also use a wild card character ‘*’ to compile all programs in the current

directory.

e.g.,javac –d c:\Tomcat 5.5\webapps\ROOT\WEB-INF\classes *.java

It is not an interesting task to type these commands many times a day. It is also

an error-prone exercise unless you have very good typing skills. You can use a

batch file (or script file in unix or linux environment) to make your life easier. A

tom.bat file can be found in the website of this book. The contents of this file are

quite simple:

javac -d c:\Tomcat 5.5\webapps\root\web-inf\classes %1.java

Format of the command to invoke the batch file is tom servlet name

The following command will compile the simple.java program with the batch

file:

tom simple

Note that there is no need to type .java.

5.6 Directories

Tomcat has a lot of sub-directories, so it is quite complicated for beginners. You

need some basic understanding of the directories and the mapping mechanism of

Tomcat.