Sel study notes

Sel study notes

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  Links: http://viralpatel.net/blogs/tutorial-spring-3-mvc-introduction- spring-mvc-framework/ http://static.springsource.org/spring/docs/2.5.x/reference/beans.html #beans-classpath-scanning 7/20/2012 @entity: The JavaPersistence API (JPA) is a POJO persistence API for object/relational mapping. It contains a full object/relational mapping specification supporting the use of Java language metadata annotations and/or XML descriptors to define the mapping between Java objects and a relational database. Here I’ll present an example of using standard JPA annotations to markup a set of POJOs and then persist the POJOs by configuring Spring to use the Hibernate AnnotationSessionFactoryBean. This example does not use the JPA API to work with persisted objects, rather, JPA annotations are only used to define the ORM mappings. Using these unaltered POJOs using the JPA API would 100% work and would almost be trivial. Dependency: To add database connectivity to the siark.com webapp I’m using a MySQL database To add database connectivity to the siark.com webapp I’m using a MySQL database and the Hibernate ORM framework. I need to add some dependencies to my pom.xml, some of which (Hibernate) are not in any of the repositories supported by Nexus in it’s out-of-the-box state. The Hibernate jar files are available from the JBoss repository. To add a new proxy repository to Nexus. 1 Log in to Nexus as an admin. 2 Select ‘Proxy Repository’ from the ‘Add’… menu. 3 Enter the ‘Repository ID’ ‘jboss’, ‘Repository Name’ ‘JBoss Repository’, ‘Remote Storage Location’ ‘http://repository.jboss.org/nexus/content/groups/public’ and press the ‘Save’ button. 4 Select the ‘Public Repositories’ from the repository list. Select the ‘JBoss Repository’ from the ‘Available Repositories’ list and add it to the ‘Ordered Group Repositories’ list. Press the ‘Save’ button. I can now add Hibernate to my pom.xml.
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  01 <dependency> 02 <groupId>org.hibernate</groupId> 03<artifactId>hibernate-core</artifactId> 04 <version>3.5.6-Final</version> 05 </dependency> 06 <dependency> 07 <groupId>org.hibernate</groupId> 08 <artifactId>hibernate-annotations</artifactId> 09 <version>3.5.6-Final</version> 10 </dependency> For some reason it’s also necessary to add javassist to the pom.xml (A Hibernate dependency that isn’t included in the dependencies!) 1 <dependency> 2 <groupId>javassist</groupId> 3 <artifactId>javassist</artifactId> 4 <version>3.11.0.GA</version> 5 </dependency> and slf4j (See http://www.slf4j.org/codes.html#StaticLoggerBinder for more options with slf4j.) 01 <dependency> 02 <groupId>org.slf4j</groupId> 03 <artifactId>slf4j-api</artifactId> 04 <version>1.5.8</version> 05 </dependency> 06 <dependency> 07 <groupId>org.slf4j</groupId> 08 <artifactId>slf4j-simple</artifactId> 09 <version>1.5.8</version> 10 </dependency> As many of the annotations used in the Hibernate POJO’s are java persistence annotations, it’s necessary to add persistence-api to the pom.xml. 1 <dependency> 2 <groupId>javax.persistence</groupId> 3 <artifactId>persistence-api</artifactId> 4 <version>1.0</version> 5 </dependency>
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  As I’m usingSpring I also need to add spring-orm. view source print? 1 <dependency> 2 <groupId>org.springframework</groupId> 3 <artifactId>spring-orm</artifactId> 4 <version>${org.springframework.version}</version> 5 </dependency> Note: A key concept in mavenSW is the idea of a repository. A repository is essentially a big collection of "artifacts", which are things like jarW, warW, and earW files. Rather than storing jars within projects (such as in a "lib" directory) on your machine, jars are stored instead in your local maven repository, and you reference these jars in this common location rather than within your projects. In addition, when you build a project into an artifact (typically a jar file), you usually "install" the artifact into your local maven repository. This enables other projects to use it. @Properties Properties are the last required piece in understanding POM basics. Maven properties are value placeholder, like properties in Ant. Their values are accessible anywhere within a POM by using the notation ${X}, where X is the property. They come in five different styles: 1. env.X: Prefixing a variable with "env." will return the shell's environment variable. For example, ${env.PATH} contains the PATH environment variable. Note: While environment variables themselves are case-insensitive on Windows, lookup of properties is case-sensitive. In other words, while the Windows shell returns the same value for %PATH% and %Path%, Maven distinguishes between ${env.PATH} and ${env.Path}. As of Maven 2.1.0, the names of environment variables are normalized to all upper-case for the sake of reliability. 2. project.x: A dot (.) notated path in the POM will contain the corresponding element's value. For example:
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  <project><version>1.0</version></project> is accessiblevia $ {project.version}. 3. settings.x: A dot (.) notated path in the settings.xml will contain the corresponding element's value. For example: <settings><offline>false</offline></settings> is accessible via ${settings.offline}. 4. Java System Properties: All properties accessible via java.lang.System.getProperties() are available as POM properties, such as ${java.home}. 5. x: Set within a <properties /> element in the POM. The value of <properties><someVar>value</someVar></properies> may be used as ${someVar}. @Spring stereotype annotations In above service layer code, we have created an interface ContactService and implemented it in class ContactServiceImpl. Note that we used few Spring annotations such as @Service, @Autowired and @Transactional in our code. These annotations are called Spring stereotype annotations. The @Service stereotype annotation used to decorate the ContactServiceImpl class is a specialized form of the @Component annotation. It is appropriate to annotate the service-layer classes with @Service to facilitate processing by tools or anticipating any future service-specific capabilities that may be added to this annotation. @Web.xml The first step to using Spring MVC is to configure the DispatcherServlet in web.xml. You typically do this once per web application. The example below maps all requests that begin with /spring/ to the DispatcherServlet. An init-param is used to provide the contextConfigLocation. This is the configuration file for the web application. <servlet> <servlet-name>Spring MVC Dispatcher Servlet</servlet-name> <servlet- class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/web-application-config.xml</param-value> </init-param> </servlet> <servlet-mapping>
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  <servlet-name>Spring MVC DispatcherServlet</servlet-name> <url-pattern>/spring/*</url-pattern> </servlet-mapping> <load-on-startup> We can specify the order in which we want to initialize various Servlets. Like first initialize Servlet1 then Servlet2 and so on. This is accomplished by specifying a numeric value for the <load-on-startup> tag. <load-on-startup> tag specifies that the servlet should be loaded automatically when the web application is started. The value is a single positive integer, which specifies the loading order. Servlets with lower values are loaded before servlets with higher values (ie: a servlet with a load-on-startup value of 1 or 5 is loaded before a servlet with a value of 10 or 20). When loaded, the init() method of the servlet is called. Therefore this tag provides a good way to do the following: start any daemon threads, such as a server listening on a TCP/IP port, or a background maintenance thread perform initialisation of the application, such as parsing a settings file which provides data to other servlets/JSPs If no <load-on-startup> value is specified, the servlet will be loaded when the container decides it needs to be loaded - typically on it's first access. This is suitable for servlets that don't need to perform special initialisation. @spring-servlet.xml The spring-servlet.xml file contains different spring mappings such as transaction manager, hibernate session factory bean, data source etc. • jspViewResolver bean – This bean defined view resolver for spring mvc. For this bean we also set prefix as “/WEB-INF/jsp/” and suffix as “.jsp”. Thus spring automatically resolves the JSP from WEB-INF/jsp folder and assigned suffix .jsp to it. • messageSource bean – To provide Internationalization to our demo application, we defined bundle resource property file called messages.properties in classpath. Related: Internationalization in Spring MVC • propertyConfigurer bean – This bean is used to load database property file jdbc.properties. The database connection details are stored in this file which is used in hibernate connection settings.
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  • dataSource bean– This is the java datasource used to connect to contact manager database. We provide jdbc driver class, username, password etc in configuration. • sessionFactory bean – This is Hibernate configuration where we define different hibernate settings. hibernate.cfg.xml is set a config file which contains entity class mappings • transactionManager bean – We use hibernate transaction manager to manage the transactions of our contact manager application @Spring Integration Spring Integration provides an extension of the Spring programming model to support the well-known Enterprise Integration Patterns. It enables lightweight messaging within Spring- based applications and supports integration with external systems via declarative adapters. Those adapters provide a higher-level of abstraction over Spring's support for remoting, messaging, and scheduling. Spring Integration's primary goal is to provide a simple model for building enterprise integration solutions while maintaining the separation of concerns that is essential for producing maintainable, testable code. @Auto-detecting components Spring provides the capability of automatically detecting 'stereotyped' classes and registering corresponding BeanDefinitions with the ApplicationContext. For example, the following two classes are eligible for such autodetection: @Service public class SimpleMovieLister { private MovieFinder movieFinder; @Autowired public SimpleMovieLister(MovieFinder movieFinder) { this.movieFinder = movieFinder; } } @Using filters to customize scanning By default, classes annotated with @Component, @Repository, @Service, or @Controller (or classes annotated with a custom annotation that itself is annotated with @Component) are the only detected candidate components. However it is simple to modify and extend this behavior by applying custom filters. These can be added as either include-filter or exclude-filter sub-elements of the 'component-scan' element. Each filter element requires the 'type' and 'expression' attributes. Five filtering options exist as described below. Table 3.7. Filter Types Filter Type Example Expression annotation org.example.SomeAnnotation An annotation to be present at the type lev
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  Filter Type ExampleExpression assignable org.example.SomeClass A class (or interface) that the target compo aspectj org.example..*Service+ An AspectJ type expression to be matched regex org.example.Default.* A regex expression to be matched by the target components' class names. custom org.example.MyCustomTypeFilter A custom implementation of the org.springframework.core. type.TypeFilter interface. Find below an example of the XML configuration for ignoring all @Repository annotations and using "stub" repositories instead. <beans ...> <context:component-scan base-package="org.example"> <context:include-filter type="regex" expression=".*Stub.*Repository"/> <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Repository"/> </context:component-scan> </beans> @Features of Spring 3.0 • Spring 3.0 framework supports Java 5. It provides annotation based configuration support. Java 5 features such as generics, annotations, varargs etc can be used in Spring. • A new expression language Spring Expression Language SpEL is being introduced. The Spring Expression Language can be used while defining the XML and Annotation based bean definition.
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  • Spring 3.0framework supports REST web services. • Data formatting can never be so easy. Spring 3.0 supports annotation based formatting. We can now use the @DateFimeFormat(iso=ISO.DATE) and @NumberFormat(style=Style.CURRENCY) annotations to convert the date and currency formats. • Spring 3.0 has started support to JPA 2.0. @J2EE Java Platform, Enterprise Edition or Java EE is Oracle's enterprise Java computing platform. The platform provides an API and runtime environment for developing and running enterprise software, including network and web services, and other large-scale, multi-tiered, scalable, reliable, and secure network applications. Java EE extends the Java Platform, Standard Edition (Java SE),[1] providing an API for object-relational mapping, distributed and multi-tier architectures, and web services. The platform incorporates a design based largely on modular components running on an application server. Software for Java EE is primarily developed in the Java programming language and uses XML for configuration. @design pattern http://www.allapplabs.com/java_design_patterns/java_design_patterns.htm @proxy server configuration http://onebyteatatime.wordpress.com/2009/04/08/spring-web-service-call-using-proxy-per- connection/#comment-71 @log4j configuration http://www.tutorialspoint.com/log4j/index.htm @Diff Struts And Spring Difference between struts and springs could be analysed from various facets. (1) Purpose of each framework. (2) Various feature offerings at framework level. (3) The design & stuff. Firstly, Struts is a sophisticated framework offering the easy 2 develop, structured view/presentation layer of the MVC applications. Advanced, robust and scalable view framework underpinning reuse and seperation of concerns to certain extent. Springs is a Lightweight Inversion of Control and Aspect Oriented Container Framework. Every work in the last sentence carry the true purpose of the Spring framework. It is just not a framework to integrate / plug in at the presentation layer. It is much more to
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  that. It isadaptible and easy to run light weight applications, it provides a framework to integrate OR mapping, JDBC etc., Infact Struts can be used as the presentation tier in Spring. Secondly, Springs features strictly associate with presentation stuff. It offers Tiles to bring in reuse at presentation level. It offers Modules allowing the application presentation to segregate into various modules giving more modularity there by allowing each module to have its own Custom/Default Request Processor. Spring provides Aspect Oriented programming, it also solves the seperation of concerns at a much bigger level. It allows the programmer to add the features (transactions, security, database connectivity components, logging components) etc., at the declaration level. Spring framework takes the responsibility of supplying the input parameters required for the method contracts at runtime reducing the coupling between various modules by a method called dependency injection / Inversion of Control. Thirdly, Struts is developed with a Front Controller and dispatcher pattern. Where in all the requests go to the ActionServlet thereby routed to the module specific Request Processor which then loads the associated Form Beans, perform validations and then handovers the control to the appropriate Action class with the help of the action mapping specified in Struts-config.xml file. On the other hand, spring does not route the request in a specific way like this, rather it allows to you to design in your own way however in allowing to exploit the power of framework, it allows you to use the Aspect Oriented Programming and Inversion of Control in a great way with great deal of declarative programming with the XML. Commons framework can be integrated to leverage the validation in spring framework too. Morethan this, it provides all features like JDBC connectivity, OR Mapping etc., just to develop & run your applications on the top of this. @SMTP http://www.code-crafters.com/abilitymailserver/tutorial_smtp.html http://www.jroller.com/eyallupu/entry/javamail_sending_embedded_image_in @nginexNginx is a fast, light-weight web server that can also be used as a load balancer and caching server. It’s been written to be able to handle an extremely large number of simultaneous connections in a very efficient manner. To be able to scale efficiently, nginx does things a bit differently than most web servers. For one, it doesn’t rely on threads to handle requests. Instead it uses a highly scalable asynchronous architecture which makes it possible for it to handle thousands of requests at once without using up a lot of system resources.
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  Nginx is freeand open source, which has made it an easy option for those looking for a small, high-performance web server. It doesn’t necessarily have to be used on its own, and many sites use it together with for example Apache for specific tasks. Nginx was developed by Igor Sysoev for use with one of Russia’s largest sites: Rambler (a web portal). He started developing the software in 2002, but the first public release wasn’t until 2004. The popularity of nginx has since exploded and it’s now used by millions of sites. A few prominent sites that use nginx in one capacity or another are WordPress.com, Hulu, and SourceForge. @ virtual machine A virtual machine (VM) is a software implementation of a computing environment in which an operating system (OS) or program can be installed and run. The virtual machine typically emulates a physical computing environment, but requests for CPU, memory, hard disk, network and other hardware resources are managed by a virtualization layer which translates these requests to the underlying physical hardware. VMs are created within a virtualization layer, such as a hypervisor or a virtualization platform that runs on top of a client or server operating system. This operating system is known as the host OS. The virtualization layer can be used to create many individual, isolated VM environments. 02 Virtual machines can provide numerous advantages over the installation of OS's and software directly on physical hardware. Isolation ensures that applications and services that run within a VM cannot interfere with the host OS or other VMs. VMs can also be easily moved, copied, and reassigned between host servers to optimize hardware resource utilization. Administrators can also take advantage of virtual environments to simply backups, disaster recovery, new deployments and basic system administration tasks. The use of virtual machines also comes with several important management considerations, many of which can be addressed through general systems administration best practices and tools that are designed to managed VMs. Note: This entry refers to the term virtual machine (VM) as it applies to virtualization technology which creates independent environments for use by operating systems and applications which are designed to run directly on server or client hardware. Numerous other technologies, such as programming languages and environments, also use the same concepts and also use the term "virtual machine". @spring 3.0 The Spring framework , created by Rod Johnson, is an extremely powerful Inversion of control(IoC) framework to help decouple your project components’ dependencies.
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  New features: http://www.mkyong.com/tutorials/spring-tutorials/ http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/new-in-3.html