What are the conceptual differences between JDK, J2EE, J2SE, and J2ME?
1.What are these?
JDK is a Java development toolkit, which is equivalent to a Java library function, and is a toolkit for compiling and running Java programs.
J2EE is Java 2 enterprise edition is a kind of enterprise version of Java for enterprise-level application service development
J2SE is Java 2 standard edition is Java standard edition, used for standard application development
J2ME is Java 2 Micro Edition is a mini version of Java, often used for development on mobile phones
J2EE, J2SE, J2ME are Java that provides different services for different uses, that is, provides different types of class libraries.
J2EE (Java 2 Enterprise Edition) for enterprise network applications, J2SE (Java 2 Standard Edition) for ordinary PC applications and
Three versions of J2ME (Java 2 Micro Edition) for embedded devices and consumer appliances
For beginners, they all start with J2SE.
2. The difference between J2EE and J2SE:
J2EE adds a series of enterprise-level application programming interfaces based on J2SE. J2EE contains a lot of technologies! There are jsp you are familiar with,
13 technologies including servlet, jdbc, jme, etc.!
J2EE is mainly used to make applications with B/S structure! That is to say, it is based on the browser and server!
J2SE gives me the feeling that only one container is needed. J2EE supports distributed components to have multiple containers at the same time.
1) What is J2EE?
J2EE is a standard proposed by Sun Company. Products that meet this standard are called "implementation"; among them, there is one of the J2EE development packages of Sun Company you downloaded.
Such "implementation", and jboss, weblogic, and websphere are all "implementations" of the J2EE standard. Because of jboss, weblogic,
The websphere itself has a J2EE API, so it can not use the J2EE implementation of sun.
2) The difference between J2EE sdk and j2sdkee
In fact, you can take J2EE sdk and j2sdkee as the same thing, the official name is J2EE sdk. But if you think carefully, you can also use the following formula
To understand: J2EEsdk is JDK, which is necessary to install ejg, j2sdkee is J2EE development environment, which is also required to install. In fact, if
If you install jboss, you don't need to install all j2sdkee. Just copy one of the files named J2EE, that is,
JDK is necessary, while j2sdkee does not need it, it depends on what you use as a container.
3. Do you still need to install J2SE sdk after installing J2EE sdk?
When downloading J2EE1.4 on sun's website, there are two types of download packages:
One is the J2EE1.4 sdk complete package (all in one), which contains J2EE server, J2SE, sample, api doc; J2EE seems to contain J2SE almost
There is something. I see that there is also a JDK in J2EE, and the lib under it is as big as the lib under J2SE (same version). But jre is not the same because J2EE is more
There are a lot more J2SE, such as java.servlet.*, java.servlet.http.*, etc.
J2EE is something you use to develop J2EE specification. If it is used for web servers, it is fine without installing J2EE, just install a jre (connection)
J2SE is not required to be installed), plus a servlet engine (such as tomcat) is enough.
Look at the following one and you can see it at a glance:
J2SE == JDK == bin + demo + include + jre + lib + src.rar //SUN's official JDK1.4.2
J2EE == JDK + .... //The JDK here is not as big as the jre file above, the reason has been mentioned above.
The other is a separate J2EE server, and you need to install J2SE sdk before installation.
No matter which one is installed, you must set the java_home, J2EE_home, classpath environment variables and then run the J2EE server.
To facilitate developers, Sun divides Java into four platforms: J2SE (Java 2 Standard Edition), J2EE (Java 2 Enterprise Edition), J2ME (Java 2 Micro Edition) and Java Card. J2SE is the foundation of all Java technologies. No matter what platform of Java applications developers want to develop, they must first learn from J2SE. J2EE technology focuses on the application of enterprise server side. J2ME is mainly aimed at embedded systems, including mobile phones, PDAs, etc. For the development of mobile applications, Sun also provides a free J2ME Wireless Toolkit. Java Card technology is used to develop applications that can be implanted into IC smart cards.
The software development kits (SDKs) of the above four platforms are all free and can be downloaded from Sun's website. Of course, using SDK alone is too unprotectable. We need development tools to improve development efficiency. Such a tool is called an Integrated Development Environment (IDE). In the past, Borland JBuilder and IBM Eclipse were the two IDEs that were most popular among Java programmers, while Sun's own IDE was unknown. After 2004, Sun placed his IDE in an important position and worked hard to promote the development of NetBeans and Java Studio. The former is an open source tool written entirely in Java, while the latter is a heavyweight official development tool. Sun's development tools are so good that Java programmers can finally be bathed in the sun!
The relationship and difference between JDK, J2EE, J2SE, and J2ME will be introduced to you here. Is it not so confusing? I hope it will be helpful for you to understand the concepts between JDK, J2EE, J2SE, and J2ME.