设计报告中英文翻译

1、ChaptersALMOST ALL APPLICATIONS MUST deal with saving and preserving data. Although some infor-mation can be stored in property files and the system environment, using a database is a natural way to ease development and increase the scalability of an application. Even if applicationisntprimarilydesi

2、gnedforstoringandcataloginginformation,itcanstillbenefithavingeasystodatastorageandDatabases are the lifeblood of many systemsChaptersALMOST ALL APPLICATIONS MUST deal with saving and preserving data. Although some infor-mation can be stored in property files and the system environment, using a data

3、base is a natural way to ease development and increase the scalability of an application. Even if applicationisntprimarilydesignedforstoringandcataloginginformation,itcanstillbenefithavingeasystodatastorageandDatabases are the lifeblood of many systems and applications, and being able understand the

4、m and manipulate them comfortably is important to the career of a engineer. Data management is such a large t a database team is egral part of medium- to large-databaseanization, and anization can have a number of In this chapter, well discuss how to connect to a database using JDBC (Java Connectivi

5、ty). Well use database for the chapter les, and well try to keep code as portable sible. (Well discuss portability and how to use complicated designsinChapters13andhisUnderstandingdatabaseUsingJavaDatabaseConnectivity Basic connection poolingAleapplicationillustratingbasicDatabaseConnectivityandBefo

6、re we look in t JDBC, lets look at the big picture. When a database starts, it requests by listening to a network port, often using TCP/IP ernetProtocol).The situationogoustoa web tstarts, listens toportand then responds to requests. However, unlike a web server, no two databases speak exactly same

7、language. Even a complex t deals with raw streams of data needs a toetheconnectiontothettranslatormechanismisadatabaseThe translation layer can be a t is o a program, or it can be ODBC(opendatabaseconnectivity)oraJDBCdriver.Compilingaoaprogramcan the most fossilized approach; however, it itable for

8、rare s when determinedinadvanceandwhentheextratime ittakestoloadadriverisLoadable drivers made available with ODBC. ODBC drivers were written in C C+,andanindividualdriverhadtobecreatedanddistributedforeachoperatingsystem.good C/C + t twists the bits of customized objects and handles huge amounts of

9、 data noeasytask.Therefore,newODBCdriverswerereleasedwhencould get them out, and if your operating system wasnt supported or supported quickly, all you could dowas get in line tocomplain.Writing drivers foreverybody was alot of work before Java.JDBC takes advantage of Javas virtual machine layer and

10、 Javas ability to produce write-once-run-anywhere code. Early on, there was a hodgepodge of JDBC drivers, many of which were hybrid ODBC/JDBC drivers. Today, every major database mak rovides pure Java database drivers.The JDBC classes and objects related to the use of JDBC are found in the java.sql

11、javax.sql HowJDBCYou mustexplicitly loada JDBC o the he JavaJDBC takes advantage of Javas virtual machine layer and Javas ability to produce write-once-run-anywhere code. Early on, there was a hodgepodge of JDBC drivers, many of which were hybrid ODBC/JDBC drivers. Today, every major database mak ro

12、vides pure Java database drivers.The JDBC classes and objects related to the use of JDBC are found in the java.sql javax.sql HowJDBCYou mustexplicitly loada JDBC o the he Java runtime YoucandosobycallingtheregisterDrivermethodon thejava.sql.DriverManager objectlikethis: DriverManager.registerDriver(

13、 new oracle.jdbc.driver.OracleDriver();Or you can use the more general dynamic class loading method java.lang.Class.forName() In both cases, the name in parentheses is the packaged ame of the driver. The -2.0.4-bin.jaronthe Class.forName registerDriverthe class to be dynamically o the Java runtime t

14、hejava.sql.DriverManagertoexplicitlyloadthenamedclass.Thes Class.forName merely t the Java runtime environment can find the amed; s of resumably signals the runtime presence of the classes. either case, a flawed or corrupted driver can still throw an exception on attempting a orperhapsafaultydriverw

15、illcauseanerror becauseitsona deprecatedmethod. Atany erformsmorerigorouschecking,anditsmorelikelytothrowanajava.sql.DriverManagerobject.Thereareseveraloverloadedfunctioncallsignaturesg a connection. Each takes a URL-based connection string, a URL string, a properties object, URL-basedconnectionstri

16、ng,andtwoadditionalstringsforusernameandLetslookatanleoftheconnectionstringandseehowitscn=This string includes the connection method ), the database driver type, machine name withthe database followedbya colon andthe port numberthe databaseis listening to, the default startup database, and another c

17、olon separating the username and password.To prevent , the his chapters code use the most explicit separation of Listing 7.1, the JdbcSetupTest JSP, tests the plain setup of database and the tshouldbe heclasspath.Figure7.1showstheresultofasfulLISTING7.1:To help you troubleshoot your JDBC installatio

18、n, the JDBC setup test page an page if an Exception is thrown. The error page, which is created in Listing 7.2, provides some troubleshooting information, and its shown in Figure 7.2.LISTING7.2:All the le . The setup of required to run the exhis chaptertyou create one databaseandfourSQLtables is det

19、ailed in Appendix A. All you need to generate the hischapteristheSQLscriptshowninListingWithout too much effort, you should be able to create All the le . The setup of required to run the exhis chaptertyou create one databaseandfourSQLtables is detailed in Appendix A. All you need to generate the hi

20、schapteristheSQLscriptshowninListingWithout too much effort, you should be able to create these tables in another database. y kept the hese chapter les simple to avoid undue hassles during tgreSQLisanotheropen-sourcetcouldalso beused for the hisAdvancedand usually expensivedatabase systems offer the

21、 ability to use stored procedures, which can be a tremendous help in factoring out SQL manipulations and building a more robust object-oriented application.Tip: Dont neglect proper database design and sane practi . If youre erested in further study, mendJoeCelkosSQLforSmartiesaufmann,1999)andC.J. Da

22、tesroductiontoSystems(Addison-Wesley1999)forathoroughexplanationofinningsofdatabaseOnce you establish a JDBC connection, you must eractions with the using s ements (java.sql.S ement ). A JDBC s ement encapsulates a single database call, a packaging of a SQL s ement. If the object already exists in t

23、he database, such as a stored procedure, use a CallableS ement (java.sql.CallableS ement). Stored procedures require an advancedunderstanding ofSQL, andwell look at the advantages of stored procedures in ements ds to the database, but query results are returned only in (java.sql.ResultSet). The resu

24、lt set object is a full-fledged Java object with lots of Each result set packages the rows returned by a ement or a ement as an item. shenextrowofaresult,callthenext()memberNote: Tos the data, youmust call the next member function of a ResultSet: next true theres data inside the ResultSet, and if th

25、e ResultSet is empty, next returns false. You must call next attemptingtoreadanyoftheOnce next() called on the ResultSet, the data values for each column are sed requestinghe header field he SQLement. For le,if the SQLquery Selectaccount_id,the datavalue issedbycallingFigure 7.3 illustrates these pr

26、inciples. To get these results, the SimpleConnect JSP Listing 7.4) requires users to this chapter.第七章 数据库enter he database tables, something we cover later 14 Java数据库连接在TCP/IP 协议14 Java数据库连接在TCP/IP 协议Control Protocol)。该过程类似WEBWEB80号端口，并且对请求进行响应。然而，与WEB服务器不同的是，数据库都使用不同的语言。即使是综合应用，ODBC（开放式数据库互联，或JDBCO