Java Learning Path process
Each person's study method is different, a person's method suits another person not necessarily, I only can discuss own study method. Because I study Java am study independently completely, has not asked others, therefore the study process basically is completely oneself tries to find out. I did not know whether this method is the quite good method, only could give everybody to provide refers.
Studies Java first step installs good JDK, writes Hello World? Actually the JDK study is not so simple, has two questions about JDK is very easy to puzzle the Java programmer continuously the place: Is the CLASSPATH question, actually said from the principle, is how must make clear JRE ClassLoader increase Class; Another question is package and the import question, how seeks the kind of way question. These two questions tried to find out clear, eliminated has studied Java and uses JDK the biggest barrier. The recommendation looked Wang Sen "the Java Depth Experiences dangers", has carried on the thorough discussion to these two questions
Second step is studies Java the grammar. The Java grammar is kind of C++, the basically mainstream programming language is not kind of C, is kind of C++, does not have what new thing, therefore the grammar study, probably was the quite a while time is enough. Only needs to pay attention is has the key words usage which several is not easy to make clear, public, protected, private, static, when uses, why has to use, how uses, this possible need some people to direct, I initially was own ponder over completely, has spent the very long time. But afterwards I saw above this book spoke these concepts to "Thinking in Java".
Third step is studies Java the object-oriented programming language characteristic place. For instance inherits, structure, abstract class, the connection, the method are many condition, heavy load, cover, Java exception handling mechanism. Said regarding a not object-oriented language background person that, I thought this process needs to spend the very long very long time, because studies in front of Java does not have C++ the experience, only then the C experience, I was have probably spent for a month, all made clear only then thoroughly these concepts, book example above repeatedly estimating, the revision, the attempt, repeatedly looked at that several chapter of contents, looked, looked has not gotten down 5, comprehended only then thoroughly. But I thought if has the C++ experience, should 12 days time be enough. Then in this process, may have a look "Thinking in Java" this book, opposite is extremely thorough to the object explanation. What a pity is I studies, has not seen to this book, therefore own have spent the massive time, and estimates through own attempt learns.
Fourth step starts a familiar Java kind of storehouse. The Java foundation class storehouse actually is JDK installs under the table of contents jre\Lib\Rt.Jar this package. The study foundation class storehouse studies rt.Jar. Inside the foundation class storehouse kind are extremely extremely many. It is said some more than 3,000, I have not counted. But said the most core truly regarding us only then 4, respectively is
Java.Lang.*;
Java.Io.*;
Java.Util.*;
Java.Sql.*;
These four packages study, each package study all may write thick teaching material, but O'reilly also truly is does this. I thought if time quite tight, is impossible through to read four books to study. I thought the quite good study method is such:
First must read through entire package the frame, understood entire package class, interface, the exception constitution, should better be can find the introduction entire package frame the article. These introduced specially package of books the first several chapters should be these overall frame content introductions. Is not must be familiar with each kind of usage to the package of overall frame assurance, which attributes remembers it have, the method. Wants to record also cannot remember. But is must know which aspects the package does have a kind of constitution, these kind of uses are any, most core several classifications maybe complete any function. I in the time which trains to the human generally is a class speaks a package, therefore not impossible detailed introduction each kind of usage, but I repeatedly stress, how do I speak these packages to you am must tell you a kind of method am transfer, also does not request you to remember the kind of method transfer, but wants you to understand, which kinds Java has provided to us, each kind is uses in any situation, when I meet the question the time, I knew which kind, or which several kind of combinations can solve my problem, That'all! When we write the procedure specifically time, so long as you knew which kind should complete your work with to be enough. Codes, the concrete method transfer, writes the code, Documentation, all things all inside Documentation, will not request you certainly to remember, are actual you also not to be able to remember more than 3,000 kinds altogether the nearly 100,000 methods transfers. Therefore changes to each package overall frame assurance extremely importantly.
Fifth step, through above study, if study the quite solid speech, built the Java foundation, is left over the work which had to do is sweeps clean inside Documentation besides above 4 packages other some comparisons to have the use the kind. Believed progressed to this step, Java studies independently the ability already to raise, might to study Documentation directly horizontal. Besides must make the GUI programming, inside JDK other can have the use the package is these:
Java.Text.*;
Java.Net.*;
Javax.Naming.*;
These packages of inside real correct uses quite many kinds very are actually few, only then several, therefore does not need to spend the very much time.
Sixth step, Java Web programming
The Web programming core is the HTTP agreement, the HTTP agreement and Java irrelevant, if not familiar HTTP agreement, although also may learn Servlet/JSP programming, but cannot achieve extrapolates, by knowing one method you will know all boundary. Therefore the HTTP agreement study is necessary. If has been familiar with HTTP agreement, also had the Java programming good foundation, studies Servlet/JSP is simply easy as pie, I study Servlet/JSP has used not to week-long time, then started with JSP to make the project. In Servlet/In the JSP study, heavy still was Servlet Documentation. Servlet the API most commonly used kind are very few, the flowered quite few time might grasp. These kinds all looked at, writes several examples to try. Servlet/The JSP programming essence is transferring these kinds to come repeatedly through the HTTP agreement converses between Web Server and Brower. Moreover to JSP, but also needs to be familiar with several commonly used JSP the mark, the concrete mode of writing cannot remember the speech, looks up temporarily and that's the end of.
In addition Java the Web programming study must place Web Application with emphasis in the design pattern, how carries on the service logic the analysis, and carries on the reasonable design, according to the MVC design pattern request, completes the different logical level separately using Servlet and JSP, how grasps carries on the flow between Servlet and JSP the control and data sharing, as well as how Web should Application dispose and the deployment.
Seventh step, J2EE programming
The above study process if is quite smooth, carries on to this step, the difficulty enhances suddenly. Because the above knowledge content all only involves an aspect, but likes EJB, JMS, core the and so on JTA J2EE standard often is several kind of Java technology synthesis utilization crystallization, therefore grasps the difficulty quite to be big.
First certainly must study good JNDI, JNDI is App the Server localization server resources (the EJB module, Datasouce, JMS) searches the method, if to JNDI not familiar, EJB, JMS these things cannot study nearly. JNDI actually is javax.Naming.* This package, utilizes is very simple. The difficulty lies in the server resources document the disposition. Regarding the server resources document disposition, needed to have a look the special documents to be standard, for instance web.Xml mode of writing, ejb-jar.Xml mode of writing and so on. In view of each kind of different App Server, but also has own service resources disposition document, also is needs to be familiar with.
Then may study JTA, mainly is must understand JTA regarding business control method, as well as should use JTA in any situation. Here may simple cite an example, we knew the ordinary circumstances may carry on business regarding a database connection (conn.SetAutoCommit (false)....,Conn.Commit ()), does is an atomic operation, but the supposition my service demand is needs to hold artificially to two different databases is an atomic operation, you can do to? At this time only could use JTA. The supposition operating process inserts a record first toward the A database, then deletes the B database another record, we wrote the code are cannot control entire hold artificially are an atomic operation. With the JTA speech, completes the control by App Server.
In studies in front of EJB must study the object sequence and RMI, RMI is the EJB foundation. Then studies JMS and EJB, said regarding EJB, most is essential is must understand how EJB is realizes through RMI to the far-end object transfer, as well as must use in any situation to EJB.
In studies EJB, after JMS these things, you possibly can realize must extremely anxiously study two domains the knowledge, is UML, another is Design Pattern. The Java enterprise software design takes the frame extremely (Framework) the design, a good software frame is the software develops the successful essential condition. In this time, should start the study key point to place the design pattern and in the frame study, experiences through the study and the actual programming grasps EJB the design pattern and the J2EE core pattern.
Inside J2EE standard, except EJB, JMS, JTA, Servlet/JSP, outside JDBC also has the very many very many enterprises technology, here 11 did not carry on introduced
Moreover also has newest domain Web Services. Web Services also completely does not have any new thing, it likes is one kind of adhesive, may unify the different service provides a unified transfer connection, said as the user, I so long as obtain the service provider for mine WSDL (to service description), has sufficed, I did not know completely the server tenderer provides actually the service is the EJB module,The Net module, any CORBA module, other any realizations, I do not need to know. Web the Services greatest place lies in through the unified service provides the way and the transfer way, has realized the entire Internet service sharing, is an extremely excited area of technology. Web Services resembles at present not to have any very good books, but may through look up the material above the network the way to study.
