There are many resources available online and in bookstores, and there are many ways to get information on J2EE. How to learn J2EE systematically and efficiently is in front of us. For example, some people still don’t know where to start when they start after reading a lot of books. Etc. These are the most difficult problems for us to deal with. How to find a good way?
In fact, if you look at it from another point of view, for example, learning English, there are three levels: vocabulary, grammar, and idiomatic usage. For example, in math class, the teacher solves problems on the blackboard, everyone is very easy to understand, there will be a lot of problems when they do it themselves. These seemingly simple problems, in fact, contain a truth: theory is linked with practice, theory guides practice.
Our theory is that we have to have good methods. Some people read a lot of books, write a lot of programs, but still improve slowly, it is difficult to overcome the difficulty. It’s a matter of method. Of course, the method I talk about is my own experience, experience, we all have their own very unique method. There is no such thing as a good or a bad way, depending on who is acting on it. So let’s focus on the methods THAT I will present in this article. Let’s make a comment.
J2EE is the present continuous tense. We know that J2EE consists of many technologies, such as EJB, XML, JDBC, RMI, JSP, Servlet,… And so on and so forth. No matter how these specific technologies evolve and change, the main thread is to grasp the essence of the J2EE architecture. The object of action is the J2EE Specification(latest version 1.4, http://java.sun.com/j2ee)!
Of course, the premise of learning J2EE is that you have enough familiarity with J2SE, and you have a good attitude and interest. It is not enough to just look at the J2EE specification. It is best to think about the products and examples. I recommend using JBuilder 7 +BEA WebLogc Platform 7.0, this development mode. Why do you say that? First of all, JBuilder 7 is good enough on its own to be a mainstream Java IDE. Second, the BEA WebLogic Platform 7.0 supports the latest version of the J2EE Specification well, and is also easy to access and widely used. Third, the development efficiency is good. Borland has a documentation of integration development for JBuilder 7 + BEA WebLogic 7.0. PDF format.) ?
JBuilder 7 itself provides a lot of help documents, both in PDF format and HTML format (made using JavaHelp technology). In addition, there are some reference books for JBuilder in bookstores, which I think are not necessary. First, the versions provided are quite old. Second, there is no content; Third, it is common to copy help documents from JBuilder itself. (Personal opinion, without any commercial purpose). Of course, your foreign language almost to have four levels, this can not have, at least reading ability is good (in fact, it is not so, I was afraid at the beginning, but began to invest, English information is also very simple, and very authentic! While improving your foreign language).
With both, we need to find the right people to learn from. Here to give a few aspects of the material to provide reference.
First, in this place of JBuilder 7 installation directory, ~ ~ : JBuilder7samplesEjbEjb20ESiteWL, there is a good example, ESite. So Session Fa is used, right? Ade design mode, using JSP, Servlet, Session Beans, Entity Beans(CMP) and other technologies, learning process do not know where can refer to the second.
Second, J2EE Tutorial data provided by http://java.sun.com/j2ee/tutorial/index.html, it is very nice, Sun’s.
Third, Java Pet Store. It was a little difficult to analyze this example by learning J2EE technology at the beginning. Moreover, the J2EE architecture in this example was not very practical, but she showed us almost all the core technologies of J2EE, and also provided a book. Design Enterprise Applications with J2EE Platform
Fourth, a better understanding of J2EE architecture, EJB,XML, JSP, Servlet and other technologies have a better understanding and program experience, I suggest reading these books. J2EE In Practice, Core J2EE Patterns, Sun Certified ENT Architect for J2Ee-Tech Study Guide, Java Tools for Extreme Programming – Wiley, EJB Design Patterns, MasteringEJB 2, Enterprise JavaBeans,3rd.
With the above foundation, combined with some experience in the project, I think the level should be improved a lot. With the basics in hand, each of us can have his or her own position in J2EE. For example, some developers can consider spending time in the business logic layer, others prefer to spend time in the presentation layer, and some greedy guys spend time in all layers of J2EE. And Web Services(the focus of the J2EE 1.4 Specification, estimated to be launched in early 2003, an important direction for the future).
There are many types of Java development platforms, and I’ll focus on J2SE as an example in this article. J2SE is a must for almost all Java application development. It is mainly composed of a Compiler, a Runtime environment, and a core API. Again, we want to emphasize that you are not writing applications that execute directly on your local operating system, but rather machine language interpreted by the JVM(Java Virtual Machine). This ensures that whether you’re developing on Solaris, Linux, Macintosh, or Windows, you can easily run on other environments or platforms.
First of all, I’d love for you to take a look at some of the Java development terms that might be helpful before you download them, and I’ve collected some of them here.
JDK: Java Develop Kit — Java development kit
J2SDK is the Java 2 Software Develop Kit
These two terms are two different names for Java platform development tools. At present, J2SDK is widely used, and the current version is 1.4.
The JRE is the Java Runtime Environment, which is generally already concentrated in the J2SDK, but if you want to run Java and not develop it, you can download the JRE directly, which is also currently version 1.4. With these concepts in mind, I’m sure you won’t be overwhelmed by J2EESDK, J2SESDK, and J2MESDK.
Now we can download it. The installer is 48.30MB, installed under C: by default, 76.2MB smaller. If you have already installed it, there is one more small setup. Open control panel?? > Advanced Settings?? > environment variables?? > System variables?? > Add a path to path. This is the path to the bin folder in your J2SDK installation. For example, you installed it in the root directory of disk D:. The path should be D: J2sdk1.4.2_03bin. With everything set, let’s start our first Java program. This time write a small applet that displays the results under a window. There are many development tools at your disposal, so we’ll just use Notepad this time. In future articles we will learn how to use specialized Java tools. First, write this code in your notepad. Notice that Java is lowercase.
Let’s open a new notepad file and write this code:
zdnetlining
Here is the output of my program:
Notice that in quotes is the file name of the *.java file you just wrote and here is Zdnetlining. Save this HTML code file as *.html, preferably with the same file name as *.java. Store the two packages in the same directory and the code writing process is complete.
Let’s take a look at the results. But before we do that, let’s look at some of the commands you can use:
Javac: This command is a compile command that allows you to compile an applet source into an. Class file for the JVM to interpret.
Appletviewer: This command is used to invoke the JVM to interpret and execute the. Class. (We’ll look at the various useful commands in more detail in a future article.)
Now we are ready to run our program.
Step 1: We open the Dos runtime (which can be found in the Resource Manager) and find your.java file. Type javaczdNetlining. Java to generate a. Class file if the compilation succeeds. Of course, nothing is displayed in Dos, but you can view this file in Windows.
Step 2: Type appletViewer zdnetlining. HTML and a window will pop up. The First Cup of Java will give you a good idea of how to write a simple applet.
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