Business-Driven Software Engineering (6.Vorlesung) Bean Interaction, Configuration, Transactions, Security Thomas Gschwind <thg at zurich.ibm.

Transcription

1 Business-Driven Software Engineering (6.Vorlesung) Bean Interaction, Configuration, Transactions, Security Thomas Gschwind <thg at zurich.ibm.com>

2 Agenda Bean Interaction and Configuration Bean Lookup References Resource Factories Configuration Transactions Basics Declarative Transaction Handling Programmatic Transaction Handling Advanced Topics EJB Security Authentication Authorization Security Propagation Demo 2

3 Agenda Bean Interaction and Configuration Bean Lookup References Resource Factories Configuration Transactions Basics Declarative Transaction Handling Programmatic Transaction Handling Advanced Topics EJB Security Authentication Authorization Security Propagation Demo 3

4 Sample EJB Component System Browsers Other Systems Messaging Clients Thick Clients HTTP Servlets/JSPs SOAP Web Services JMS RMI-IIOP RMI-IIOP RMI-IIOP Application Server Message Driven Bean Session Bean Session Bean Entity Bean Session Bean Entity Bean Session Bean 4

5 Bean Lookup Option 1: Use JNDI similarly as used by clients Use the session context to look up a bean More efficient, since no InitialContext object needs to be SessionContext context; OtherBean bean = (OtherBean) context.lookup(otherbean.class.getname()); Option 2: In EJB 3.0, use OtherBean bean; 5

6 Bean Customization Environment Properties Stored in Deployment descriptor <env-entry> <description>order in which quotes are returned.</description> <env-entry-name>quoteservice/order</env-entry-name> <env-entry-type>java.lang.string</env-entry-type> <env-entry-value>text</env-entry-value> </env-entry> 6

7 Bean Customization (cont d) Option 1: Again use JNDI Use the session context to look up a bean More efficient, since no InitialContext object needs to be SessionContext context; String order=(string) context.lookup("java:comp/env/quoteservice/order"); Option 2: In EJB 3.0, use = "QuoteService/order") String order; 7

8 Resource Factories Necessary for calling external resources Acquiring database connections JCA adapters Looked up through Context (similar to references) Use resource injection For EJB 3.0 entities, use persistence units 8

9 Agenda Bean Interaction and Configuration Bean Lookup References Resource Factories Configuration Transactions Basics Declarative Transaction Handling Programmatic Transaction Handling Advanced Topics EJB Security Authentication Authorization Security Propagation Demo 9

10 Why Transactions? Series of statements that execute like a single one Naive implementation Need to consider every possible error Error handling out of control (eg, network failures) Testing challenge try { // withdraw funds from // account 1 } catch(exception e) { // handle error return; } try { // deposit funds to // account 2 } catch(exception e) { // redeposit to account 1 // handle error return; } 10

11 Transactions Advantages Guarantee all-or-nothing execution Allow concurrent access to data Using Transactions Explicit middleware Programmed Implicit middleware Declarative 11

12 Transaction Properties Atomicity All or no statements will be executed In a distributed setting, achieved by voting Consistency Inconsistencies while transaction is running are OK No inconsistent state after transaction commits Isolation Changes from one transaction only visible after commit Achieved by locking database Durability Updates survive crashes Achieved using logs 12

13 Transactional Models Flat Transactions On abort no statement is executed Invalid parameters Constraint violation Failure On commit, all statements are executed 13

14 Transactional Models (cont d) Nested Transactions On abort, only nested transaction is rolled back Allows to find alternatives to complete transaction Ideal for long running transactions On commit only nested transaction completes Commit/rollback of global transaction => commit/rollback of nested transactions Not supported by EJB 14

15 Isolation Properties Read Uncommitted Read Committed Repeatable Read Serializable Definition of isolation properties not standardized 15

16 Distributed Transactions When? Multiple application servers Updates to different databases Whenever you have different communication partners How? Use a distributed transaction manager Two phase commit Phase one: send prepare Phase two: send commit/rollback No interoperability between application servers 16

17 Programmatic vs. Declarative Transactions Programmatic (bean-managed) Good if several smaller transactions required More powerful Only available for Session & Message Driven Beans Declarative (container-managed) Easy to use 17

18 Agenda Bean Interaction and Configuration Bean Lookup References Resource Factories Configuration Transactions Basics Declarative Transaction Handling Programmatic Transaction Handling Advanced Topics EJB Security Authentication Authorization Security Propagation Demo 18

19 Declarative Transactions EJB Container/Server Client 2. begin 1. transfer() Transaction EJB Object 5. commit/ Service abort 3. delegate <transaction-type> Container </transaction-type> Enterprise Bean 4.Business ops. 19

20 Declarative Public class BankBean implements BankRemote private EntityManager private SessionContext ctx; public void transfer(double amount, String from, String to) { // } 20

21 Declarative Transactions: Deployment Descriptor <assembly-descriptor> <container-transaction> <method> <ejb-name>tellerbean</ejb-name> <method-name>*</method-name> </method> <trans-attribute>required</trans-attribute> <container-transaction> <container-transaction> <method> <ejb-name>tellerbean</ejb-name> <method-name>deposit</method-name> <method-param>double</method-param> </method> <trans-attribute>required</trans-attribute> <container-transaction> </assembly-descriptor> 21

22 Transaction Attributes Required RequiresNew Supports Mandatory NotSupported Never 22

23 Controlling Transaction-Length EJB Container/Server Client 2. begin 1. transfer() Teller Transaction 6. commit/ EJB Object Service abort 3. delegate Teller Bean 4. withdraw 5. deposit <trans-attribute> Required </trans-attribute> Account 1 Account 2 23

24 Aborting a Transaction public void deposit(double amt) { balance+=amt; } public void withdraw(double amt) { if(balance-amt<creditline) ctx.setrollbackonly(); else balance-=amt; } Transaction may be aborted using ctx.setrollbackonly() Identify whether a transaction is in the aborted state with ctx.getrollbackonly() 24

25 Programmatic Transactions Client 1. method() EJB Container/Server Transaction Service EJB Object 2. delegate 3. begin Enterprise Bean 5. commit/ abort <transaction-type> Bean </transaction-type> 4.Business ops. 25

26 Programmatic Transactions (cont d) Use Java Transaction API (JTA) public interface javax.transaction.usertransaction { public void begin(); public void commit(); public int getstatus(); public void rollback(); public void setrollbackonly(); public void settransactiontimeout(int tmo); } 26

27 Programmatic Transactions private UserTransaction ut; public void deposit(double amt) throws AccountException { try { ut.begin(); balance+=amt; ut.commit(); } catch(exception e) { if(ut!=null) ut.rollback(); throw new AccountException("Error: "+e.getmessage()); } } 27

28 Programmatic Transactions (Ex.) public void deposit(double amt) throws AccountException { UserTransaction ut=null; try { ut=ctx.getusertransaction(); ut.begin(); balance+=amt; ut.commit(); } catch(exception e) { if(ut!=null) ut.rollback(); throw new AccountException("Error: "+e.getmessage()); } } 28

29 Agenda Bean Interaction and Configuration Bean Lookup References Resource Factories Configuration Transactions Basics Declarative Transaction Handling Programmatic Transaction Handling Advanced Topics EJB Security Authentication Authorization Security Propagation Demo 29

30 Transactional Callbacks Allows bean to react to committed/rolled back transactions Bean has to implement javax.ejb.sessionsynchronization interface afterbegin() beforecompletion() aftercompletion(boolean) true => commit, false => rollback Only for transactional, stateful, CMP session beans 30

31 Doomed Transactions Sometimes obvious that transaction cannot commit => Doom transaction Cont. managed => ctx.setrollbackonly() Bean managed => usertransaction.setrollbackonly() Overhead if statements until commit are executed => Query for doomed transactions Cont. managed => ctx.getrollbackonly() Bean managed => usertransaction.getstatus() 31

32 Client-Initiated Transactions Client 1. begin() 5. commit/abort() EJB Container/Server Transaction Service 2. method() EJB Object 3. delegate Enterprise Bean 4.Business ops. 32

33 Transactions from Client Code try { Properties props=system.getproperties(); Context ctx=new InitialContext(props); ut=(usertransaction) ctx.lookup("java:comp/usertransaction"); ut.begin(); // invoke server-side methods ut.commit(); } catch(exception e) { } Useful if client needs to identify commit Client-initiated distributed transactions Be careful! Performance! 33

34 Agenda Bean Interaction and Configuration Bean Lookup References Resource Factories Configuration Transactions Basics Declarative Transaction Handling Programmatic Transaction Handling Advanced Topics EJB Security Authentication Authorization Security Propagation Demo 34

35 EJB Security Java Authentication & Authorization Service (JAAS) Who am I? What may I? For Session and Entity beans Client Machine 1. Login Servlet/JSP Java App. Portable 4. Invoke JAAS API Vendor specif. logic Propietary Provider 2. Call server J2EE Server 3. Authenticate FooSecurity Inc. EJB Component 35

36 Authentication Client 5 6 Subject Action LoginContext 2 3 Configuration Login Module 3 J2EE Server 36

37 Authentication (cont d) Red: 1.Invoke new 2.Invoke new and getappconfigurationentry 3.Return list of LoginModules 4.Invoke new and initialize Blue: 1.Invoke getsubject 2.Invoke login 3.Authenticate with proprietary API 4.Invoke getsubject and receive subject 5.Invoke new 6.Invoke doas(subject, action) 7.Invoke run 8.Perform operation (invoked via the network) 37

38 Authorization Client Side public class QuoteClient { private static LoginContext logincontext = null; public static void login(string u, String p) throws LoginException { logincontext=new LoginContext("QuoteService", new UsernamePasswordHandler(u, p.tochararray())); logincontext.login(); } public static void logout() throws LoginException { logincontext.logout(); } public static void main(string[] args) throws Exception { Context ctx=new InitialContext(System.getProperties()); login(args[0],args[1]); QuoteServiceRemote quoteservice = (QuoteServiceRemote) ctx.lookup("quoteservice/remote"); 38

39 Authorization Client Side (cont d) The QuoteService login context needs to be defined The login context is retrieved from the file specified in the java.security.auth.login.config system property QuoteService { org.jboss.security.clientloginmodule required; }; -Djava.security.auth.login.config=login.config 39

40 Authorization Server Side Declarative Authorization Security logic defined in deployment descriptor May be changed more easily Programmatic Authorization Beans interlaced with security logic More powerful 40

41 Declarative user"}) public class QuoteService implements public Quote addquote(string text) { System.out.println("QuoteService.addQuote("+text+")"); if (ctx.getrollbackonly()) return null; Quote quote = new Quote(text); em.persist(quote); return quote; } } 41

42 Declarative Authorization Specifying permissions in the deployment descriptor <ejb-jar> <enterprise-beans> </enterprise-beans> <assembly-descriptor> <method-permission> <role-name>administrators</role-name> <method> <ejb-name>cookie</ejb-name> <method-name>*</method-name> </method> </method-permissions> 42

43 Declarative Authorization (cont d) <method-permission> <role-name>guests</role-name> <method> <ejb-name>cookieserver</ejb-name> <method-name>getcookie</method-name> <method-params>int</method-params> </method> </method-permissions> <exclude-list> <method> </method> </exclude-list> </assembly-descriptor> </ejb-jar> 43

44 Programmatic Authorization EJB context allows programmer to get authentication information Authorization may be performed on User information Roles Security roles defined in deployment descriptor public interface javax.ejb.ejbcontext { public java.security.principal getcallerprincipal(); public boolean iscallerinrole(string role); 44

45 Programmatic user"}) public class QuoteService implements QuoteServiceRemote, { public void updatequote(long quoteid, String text) { Quote quote = findquote(quoteid); String name = ctx.getcalleridentity().getname(); if(!ctx.iscallerinrole("administrators") &&!name.equals(quote.getowner())) { throw new SecurityException( "only admins and quote owner allowed to change quote"); } // change text of cookie } } 45

46 Users and Roles Where does the other SecurityDomain store users and roles? users.properties username = password roles.properties username = role1, role2, Other authentication modules exist that store user information in a database 46

47 Security Propagation How are security credentials passed between beans? Client credentials? Other credentials? Defined with annotation or in the Deployment Descriptor <entity> <ejb-name>cookie</ejb-name> <security-identity> <use-caller-identity> </security-identity> <security-identity> <run-as> <role-name>admins </role-name> </run-as> </security-identity> 47

48 Agenda Bean Interaction and Configuration Bean Lookup References Resource Factories Configuration Transactions Basics Declarative Transaction Handling Programmatic Transaction Handling Advanced Topics EJB Security Authentication Authorization Security Propagation Demo 48

49 Summary Bean Interaction and Configuration Bean Lookup References Resource Factories Configuration Transactions Basics Declarative Transaction Handling Programmatic Transaction Handling Advanced Topics EJB Security Authentication Authorization Security Propagation Demo 49

50 Review Questions Explain the ACID properties Explain the different isolation properties Explain the EJB transaction attributes How can you control the transaction length with the transaction attributes, give examples Explain the difference between container managed and bean managed transactions How do you set a transaction to be rollback only How do you check whether a transaction is rollback only and why would one need this Explain the difference between declarative and programmatic security management 50

51 Tasks 1. Experiment with the sample fro this lecture 2. Deactivate security in the client and connect to the server 3. Try logging in with an incorrect user/role 4. Play with the maxquotes parameter to trigger a rollback of the transaction 51

52 Outlook EJB Web Services Implementing Web Services with Session Beans Message-Driven Beans 52