通向架构师的道路之漫谈使用threadlocal改进你层次划分

1、ThreadLocal 很容易让人望文生义，想当然地认为是一个“本地线程ThreadLocal 很容易让人望文生义，想当然地认为是一个“本地线程”。其实，ThreadLocalJava的新发明，很多语言（IBM IBM XL FORTRAN）在语法层面Java 开发者中得到很好的普及。ThreadLocal的接ThreadLocal4 voidset(Object public Object publicvoidJDK5.0 protected 1get()set(Object)1次。ThreadLocalnullJDK5.0 中，ThreadLocal 已经支持泛型，该类的类名已经变为 Th

2、readLocalAPIAPI方法分别是voidset(Tvalue)、 T get()T initialValue()。2.1Service2.1Service方法中调用多方可以看到有一个Service方法，在该Service方法中调用多 Service 方法中的的该Service 方法结束后，提交事务；Service2.2可以看到有一个Service方法，在该Service方法中调用多 Service 方法中的的该Service 方法结束后，提交事务；Service2.2传统的做Service层代码publicvoidserviceMethod() Connection conn=null

3、;Connection123每层的代码每层的代码private Connection conn=null; 1(Connectionconn)public void doSomething() ementpstmt=null; catch(Exceptionlog.error(e,”Execeptionoccurredcatch(Exceptione) catch(Exceptioncatch(Exceptione) catch(Exception如果我一个Service方法有调用一如果我一个Service方法有调用一则，如果有一多关了一个conn，那就会导致其它的connnull 笔者曾经遇

4、见过2个项目出现outofmemory或者是connectionpoolhasbeenleakage，中多关或者在service 层中漏关，或者是每个conntionconn=getConnection()connectio（关个P 关！）。当然，如果你说你在写法上绝对promise 绝对注意这样2.3Spring中的做SpringSpringServicepublicvoidserviceMethod() /aop 自动加入connection，并且catch(Exception/aop /aop自动加/aop catch(Exception这这 的写方法，service方法，不需要关心在哪

5、边commit哪rollback何时connection，spring式事务会负责，这种风 Service层的方开启事务（如果讲究点的还会设一个 在该Service 层中的所有使用该service 方法中开启的事务（即connection）； 层中如果发生错误就抛回Service 层 Serviceexceptioncatchrollbacktrycommitfinally块中connection。这。就举个更实际的例子再次来说明 3个用户 同一个 serviceservice3个 方法为一个完整事务，那么整个web 容器内只因该有3 connection，并且每个connection 之间的

6、状态，彼此“ ”。下面一起来看 如何用代码实现类似于Spring的这种做法首先，根的ThreadLocal的概念 2.4ThreadLocalpublicclassConnectionManagerprivate sicThreadLocaltl=newThreadLocal(); private sic Connection conn = null;public sic void Begrans)throwsException if (tl.get() = null | (Connection) tl.get().isClosed() conn=SingletonDBConnection.g

7、etInstance().getConnection(); conn = new ConnectionSpy(conn);if rans)public sicConnectiongetConnection()throwsException return (Connection) tl.get();2.5利用ThreadLocal2.5利用ThreadLocal改造ServiceService 层（注意红色标粗-好粗 yeah，的地方packagepublicclassStudentServiceImplimplementsStudentService publicvoidaddStudent(

8、Studentstd)throwsExceptionpublic sicvoidclose()throwsSQLException try (Connection)catch(Exceptione)(Connection)tl.get().close(); public sicvoidcommit()throwsSQLException try (Connection)catch(Exceptione)try(Connection)catch(Exceptione)public sicvoidrollback()throwsSQLException try (Connection)catch(

9、Exceptione)try(Connection)catch(Exceptione) SpringService方法就诞生了？2.6使用ThreadLocal分离Service先来看表结T_Student= new Student = new ClassRoomtry catch(Exceptione)trycatch(Exceptionde)thrownewfinallytrycatch(Exceptione)需求很简单，T_ClassRoom表里已经有值了，在 T_Student表的数据时同时要给这个学生分配一个班级并且需求很简单，T_ClassRoom表里已经有值了，在 T_Stude

10、nt表的数据时同时要给这个学生分配一个班级并且 T_Student_ClassRoom表，这就是一个事务，这两步中有任何一步看来工程的结构吧 T_ClassRoom2.6.1ConnectionManagerpackagemportpublicclassConnectionManagerprivates privatepublicicThreadLocal2.6.1ConnectionManagerpackagemportpublicclassConnectionManagerprivates privatepublicicThreadLocaltl=newicConnectionconn=i

11、cvoidrans)throwsExceptionif(tl.get()=null|(Connection)tl.get().isClosed()conn =ifrans)2.6.2DBConnection2.6.2DBConnectionpublic sicConnectiongetConnection()throwsException return (Connection) tl.get();public sicvoidclose()throwsSQLException try (Connection)catch(Exceptione)(Connection)tl.get().close(

12、); public sicvoidcommit()throwsSQLException try (Connection)catch(Exceptione)try(Connection)catch(Exceptione)public sicvoidrollback()throwsSQLException try (Connection)catch(Exceptione)try(Connection)catch(Exceptione)packagepublicclassDBConnectionprivates privates privates privates privates privatep

13、ackagepublicclassDBConnectionprivates privates privates privates privates privateprivateicDBConnectioninstance=icStringame=icStringconnectionUrl=null; ic String userName = null;ic String password = null; icConnectionconn=null;icPropertiesjdbcProp=privateDBConnection()private sicPropertiesgetConfigFr

14、omPropertiesFile()throwsException Properties prop = null;prop=JdbcProperties.getPropObjFromFile(); return prop;privateicvoidinitJdbcParameters(Propertiesprop)ame=connectionUrl=prop.getProperty(Constants.CONNECTION_URL); userName = prop.getProperty(Constants.DB_USER_NAME);password=privateicvoidcreate

15、Connection()throwsExceptionconn=DriverManager.getConnection(connectionUrl,userName,public sicConnectiongetConnection()throwsException return conn;public synchronized sicDBConnectiongetInstance()throwsException if (instance = null) jdbcProp=getConfigFromPropertiesFile(); instance = new DBConnection()

16、;2.6.3JdbcPropertiespackage sky.2.6.3JdbcPropertiespackage sky.mport java.io.File;mport mportjava.io.FileNotFoundException; mport java.io.IOException;mportjava.io.InputStream; mport .URL; mport java.util.*;publicclassJdbcPropertiesprivate sicLoglogger=LogFactory.getLog(JdbcProperties.class); public

17、sic Properties getPropObjFromFile() Properties objProp = new Properties(); ClassLoaderclassLoader=Thread.currentThread()URLurl=classLoader.getResource(Constants.JDBC_PROPERTIES_FILE); if (url = null) classLoader=url=Filefile=newFile(url.getFile(); InputStream inStream = null; try inStream=newFileInp

18、utStream(file); catch(FileNotFoundExceptione) objProp = null; catch (IOException e) return instance;2.6.6StudentServiceImplpackage sky.mport java.util.ArrayList; mport java.util.List;mport mport sky.mport sky.6StudentServiceImplpackage sky.mport java.util.ArrayList; mport java.util.List;mport mport

19、sky.mport sky.2.6.5StudentService接package sky.mport java.util.List; mport java.util.Vector; mport sky.tudentServicepublicvoidaddStudent(Studentstd)throws2.6.4Resource目录下的finallytry if(inStream!=null)inStream = null;catch(Exceptione)return2.6.7接2.6.7接package sky.mportjava.util.HashMap; mport java.uti

20、l.List;mport sky.mport sky.mport sky.mport sky.publicclassStudentServiceImplimplementsStudentServicepublic void addStudent(Student std) throws Exception = new Student= new ClassRoomtry catch(Exceptione) try catch(Exceptionde)thrownewfinallytry catch(Exceptione)2.6.8Impl2.6.8Implpackagemportjava.sql.

21、*; mport mport sky. mport sky.publicclassImplimplementspublicvoidaddStudentClassRoom(StringroomId,StringsNo)throwsException Connection conn = null;ementpstmt=null; try conn=ConnectionManager.getConnection(); pstmt = connpstmt.setString(1,roomId); pstmt.setString(2, sNo); catch(Exceptione)thrownewExc

22、eption(addStudentClassRoom:+e.getMessage(),finallytry if(pstmt!=null)pstmt = null;catch(Exceptione)erfacepublicvoidaddStudentClassRoom(StringroomId,StringsNo)throws2.6.10Implpackage.mportmportmportsky. mportmport ;mport java.util.List; mportjava.util.ArrayList; mport java.util.Vector;mportmport publ

23、icclassImplimplementsoglogger2.6.10Implpackage.mportmportmportsky. mportmport ;mport java.util.List; mportjava.util.ArrayList; mport java.util.Vector;mportmport publicclassImplimplementsoglogger=publicvoidaddStudent(Studentstd)throwsException.2.6.9接package sky.mport java.util.*;mport sky.publicvoida

24、ddStudent(Studentstd)throws.Connection conn = null; ementpstmt=null; try conn =pstmt = conn.prepareSConnection conn = null; ementpstmt=null; try conn =pstmt = conn.prepareSpstmt.setString(1, std.getsNo(); pstmt.setString(2, std.getsName(); pstmt.setString(3, std.getsAge();pstmt.setString(4,pstmt.set

25、Date(5,catch(Exceptione)thrownewException(addStudent:+e.getMessage(),finallytry if(pstmt!=null)pstmt = null;catch(Exceptione)publicvoiddelStudent(StringsNo)throwsException Connection conn = null;ementpstmt=null; try conn =pstmt = conn.prepareSpstmt.setString(1, sNo); catch(Exceptione)thrownewExcepti

26、on(delStudent:+e.getMessage(),2.6.12SqlpackagepublicclassSql publicicStringADD_STUDENT_CLASSROOM=o2.6.13ClassRoompackage2.6.12SqlpackagepublicclassSql publicicStringADD_STUDENT_CLASSROOM=o2.6.13ClassRoompackagemport publicclassClassRoomimplementsSerializableprivateStringroomId=.2.6.11Sqlpackage sky.

27、public class StudentSqlpublic final sic String ADD_STUDENT = insertot_student(sno,sname,sage, finallytry if(pstmt!=null)pstmt = null;catch(Exceptione)2.6.14Studentpackagemport 2.6.14Studentpackagemport publicclassStudentimplementsSerializablepublicStringgetsNo() return sNo;publicvoidsetsNo(StringsNo

28、) o = sNo;publicStringgetsName()privateStringroomName=publicStringgetRoomId() return roomId;publicvoidsetRoomId(StringroomId) this.roomId = roomId;publicStringgetRoomName() return roomName;publicvoidsetRoomName(StringroomName) this.roomName = roomName;returnpublicvoidsetsName(StringsName)amereturnpu

29、blicvoidsetsName(StringsName)ame=publicStringgetsAge() return sAge;publicvoidsetsAge(StringsAge) this.sAge = sAge;publicStringgetGender() return gender;publicvoidsetGender(Stringgender) this.gender = gender;private String sNo = ; privateStringsName=; private String sAge = ; privateStringgender=; pri

30、vate String sbirth = ;privateStringclassRoomId=privateStringclassRoomName=publicStringgetClassRoomId() return classRoomId;2.6.15StudentCRUD类（运行主类package2.6.15StudentCRUD类（运行主类packagemport mport mport publicclassStudentCRUDpublicvoidaddStudent()throwsExceptiontdService=newStudentServiceImpl(); Studen

31、t std = new Student();publicvoidsetClassRoomId(StringclassRoomId) this.classRoomId = classRoomId;publicStringgetClassRoomName() return classRoomName;publicvoidsetClassRoomName(StringclassRoomName) this.classRoomName = classRoomName;publicStringgetSbirth() return sbirth;publicvoidsetSbirth(Stringsbir

32、th) this.sbirth = sbirth;Hibernate在事务操作中也支持ThreadLocal 这边指的是不用Spring，Hibernate3与的区ServiceHibernate在事务操作中也支持ThreadLocal 这边指的是不用Spring，Hibernate3与的区Service。publicicvoidmain(Stringargs)StudentCRUDtestStudentCRUD=newStudentCRUD(); try catch(Exceptione)三、Hibernatefinally这时如果用的是caseServicehb 1.doSomething

33、(); hbfinally这时如果用的是caseServicehb 1.doSomething(); hb 2.doSomething(); hb publicvoidtestUser()throwsExceptioniontran=Factoryfactory= = new Usertry factory = HibernateUtil.getInstance().getSes= factory.openSestran = sesTUser testUser = new TUser();catch(Exceptione) thrownewfinallycatch(Excepton自己用Thr

34、eadLocal 模式写一个SesManagement 类，来这个ses自己用ThreadLocal 模式写一个SesManagement 类，来这个ses把在Service方法中打开的，传到每方法中，使每方法使用同一Service方法中去关闭它（很烂的做法）下来看看Hibernate自身提供的3.1.2要使用这个getCurrentSes，你的hibernate的设置必须如下（红色加粗部分显示-就喜欢粗J）：?xml =1.0encoding=UTF-!DOCTYPEhibernate-configuration-/Hibernate/HibernateConfigurationDTD propertypropertyproperty propertyproperty/TUser.hbm.xmlpublicvoidtestUser()throwsExceptioniontran=publicvoidaddUser(TUseruser)throwsExceptionFactorypublicvoidaddUser(TUseruser)throwsExceptionFactoryfactory= factory.getCurrentSes3.1.3