Research of Structure Integration based on Struts and Hibernate

Transcription

1 2009 World Congress on Computer Science and Information Engineering Research of Structure Integration based on Struts and Hibernate Juanjuan Yan,Bo Chen,Xiu-e Gao,Le Wang Information Engineering College,Dalian University,Dalian Liaoning, China Abstract Struts framework based on MVC has brought the best code reuse and the legible code structure in entire system by far, but it has some problems such as complicated program, high coupling among layers and hard maintenance because its model part adopts JDBC to connect databases directly. The ORM characteristics of Hibernate make it simple and easy to implement the transplant and manipulation of databases. The development and maintenance of entire system become easier because of these characteristics. This paper proposed the integration of Struts and Hibernate and showed a simple system to explain the advantages of the integration. 1. Introduction Following the rapid development of network technique, the distributed enterprise Web application technique is becoming mature day by day. With the extensive application of Java technology, the Web application system of Java 2 Platform Enterprise Edition (J2EE)[1] is accepted by the great majority companies gradually for its stratification and the independence of platform. J2EE has been testified to be a trusting enterprise technique of software development and supported by many important firms of IT industry. But J2EE has some disadvantages, for instance, the high price, long periods and complex realization which bring from Enterprise Java Bean(EJB). Now Struts has already become the most popular framework based on Java language because of bringing the excellent layer division to Web application. At present, a few large-scale firms embed Struts in J2EE of the assembly development implement. But in the model part of Struts the realization of the interaction between system and database is not ideal. While Hibernate provides the mapping mechanism from Java class to datasheet, the data inquiring and recovering mechanism and so on, and it realizes the object permanence of data layer. Hibernate gets rid of the disadvantages of operating the relational database in system directly. Therefore, adopting the multi-layer framework of integration based on Struts and Hibernate can bring the both merits to play sufficiently which solves some disadvantages of the traditional J2EE well. 2. Struts Framework Based on MVC In the traditional Web application, Java Server Pages(JSP) pages are responsible for handling all things, for example, receiving requests, executing business logics, choosing the next page. These complicated things may lead to chaos of JSP pages codes and be harmful for the extension and maintenance of pages. The Model-View-Controller (MVC)[1] mode separates the programming codes into three different areas, which has solved the above problem. MVC can realize J2EE application system's stratification and the loose coupling of three layers or multilayer, and it is a realization way of orienting dynamic content. The MVC mode divides application into three core components of Model, View and Controller. Struts is a realization of MVC. It is an open source Web application framework and uses Servlet and JSP marks that belong to the J2EE norm as a part of the realization. Struts inherits MVC characteristics and realizes some corresponding changes and extension according to J2EE traits. Struts separates Java codes of JSP by Java Bean and Action class to be the MVC mode, transmits data among the three partitions of Model, View and Controller, demonstrates the connection between various classes and JSP pages by configuration files finally and it intends to realize the separation of presentation layer, business layer and data layer. The Struts structure is shown in Figure 1. The Model contains the business logic that exchanges data with a persistence layer. The View is in charge of producing what is directly visible to the user, e.g. web pages. The Controller is the layer that receives requests from clients, determines what business logic takes place and where to go next. In the Struts framework, the Model uses Java classes for the business logic. The View can be implemented with JSP and the Taglib of Struts. The Controller is a J2EE component known as Servlet, more specifically an ActionServlet object, which determines what or when logic gets executed and where the control should get directed. The research is sponsored by IT industry bureau of Dalian (No ) /08 $ IEEE DOI /CSIE

2 Event Controller ActionServlet Http Request Dispatch Business Logic (Action) application server, and nearly support all popular databases server. 3.2 Principle of Hibernate Client (Browser) Update Http Response Struts-Taglib Forward View (JSP) Struts-config.xml Get Figure 1. Struts structure Model (Application State) Application Resource 3. Hibernate Framework Based on ORM Working with both the object-oriented software and the relational database is a complicated task with Java Database Connectivity (JDBC) because there is mismatch between how data is represented in objects versus relational database. So with JDBC, developers have to write pure the Structured Query Language (SQL) statements to map an object model's data representation to a relational data model and its corresponding database schema Introduction of Hibernate Hibernate is a flexible and powerful Object- Relational Mapping (ORM)[2] solution to map Java classes to database tables. It is a powerful, high performance object-relational persistence and query service. Hibernate allows developers to express queries in its own portable SQL extension (Hibernate Query Language (HQL))[3], as well as in native SQL, or with an object-oriented criteria and example Application Programming Interface(API). Hibernate itself takes care of this mapping using XML files so developers don t need to write code for this. Hibernate is an open source and it is free to use for both development and production deployments, which is a bridge between Java application and relational database and takes charge of mapping between Java objects and relational data. The inside of Hibernate packs the operation of accessing database by JDBC, which provides API of object-oriented database access to upper layer application. So developers can use the object programming thought to operate database sufficiently, caring for the bottom database structure unnecessarily. Hibernate relieves the developer from 95 percent of common data persistence related programming tasks, compared to manual coding with SQL and the JDBC API[4]. And it can integrate various Web server or Application Persistent Objects Hibernate Hibernate.properties XML.Mapping Database Figure 2. Hibernate systematic structure As shown in figure 2, Hibernate lies in the middle layer that is between application and database. In the provided persistent service, Hibernate maps class to rows of datasheet by properties and mapping files of class (mapping.xml) itself. Application interacts with database by Persitstent Object (PO) to handle data directly. 4. The Integration of Struts and Hibernate In the open source frameworks, for the presentation part, Tapestry[2] has the powerful and natural combination of pages, its document is too conceptional to benefit programming. And its learning curve was too steep and so on. For the logic part, Spring has a good integration function, but there is a lack of public controller. And EJB[2] depends on the EJB containers, at the same time, it is realized complicatedly. While Struts has been applied extensively because of its advantages. At present, most of systems apply the relational databases mainly, while Java is an object-oriented language essentially. In Model part of Struts framework application, using SQL and JDBC to operate databases when storing and fetching objects reduces programming efficiency and the systematic maintainability. Traditional J2EE-based application applies heavyweight framework based on EJB that adapts to the large enterprise development, while development and debugging by EJB container need to consume a plenty of time and high price. EJB3 improves the disadvantages of original EJB, but its application is not mature yet. Hibernate can substitute Container-Managed Persistence (CMP) to accomplish heavy responsibility of permanence in J2EE framework of applying EJB[3]. In a word, Hibernate can resolve the difficulties coming from using traditional CMP, JDBC and Data Access Object(DAO)[5] in a technological development. For reducing the coupling of code and raising systematic development efficiency, this paper suggests J2EE 531

3 application development tactics based on Struts and Hibernate. The Struts design shows the MVC framework sufficiently, which all control flows need a configuration file (Struts-config.xml) to manage, and which is convenient to maintain. The integration of Struts and Hibernate is that Hibernate solves the model layer of Struts, which makes developers operate Java objects instead of database. The integration shows the object-oriented thought sufficiently and solves some problems of the database operation in traditional J2EE well Flow of Framework The flow of integration framework based on Struts and Hibernate is shown in Figure 3[6]. At first, users send Http requests by Browser, then Http requests are accepted by ActionServlet of the control component in business layer, then gave to RequestProcessor which gets corresponding Action from ActionMapping by request URL[3]. Besides, ActionForm packs JSP pages, which can make a checking to data of datasheet if it is needed, send back ActionErrors to visual pages if there are mistakes and transfer the data of pages to Action if it passes validation. RequestProcessor transfers the execute method of Action and the method transfers the business logic module. Hibernate accomplishes interaction of databases and JavaBean. The operation of processing business logic interacts with database by data permanence layer and field object layer. The execute method of Action will return ActionForward objects that are accepted by ActionServlet after executing. Thereby, ActionServlet is transmitted to the appointed resource of ActionForward, which means the correct view chosen is shown to users Systematic Structure of the Integration Framework The EIS layer of the multi-layer J2EE systematic structure can be partitioned into the data permanence layer[7] and the data resource layer. It means a system can be divided into five layers as a whole: Client Layer: This layer runs in the Browser of users machines and handles interaction with users, transmits and shows messages to users. J2EE platform supports different type users including HTML users, Java Applets, Java application, etc. Presentation Layer: This layer works in J2EE Web container, produces the systematic representation logic, handles users requests and makes the responses. The entire Web is built on Struts framework, in which the View component is composed of JSP/HTML pages whose data is expressed by ActionForm Bean, the Controller component is composed of ActionServlet united Struts-config.xml and Action Classes, and the Model component is realized by business logic layer. Business Logic Layer: This layer accomplishes the required business of system, provides the required business method to presentation layer. It can receive data from client programs and save them to the storage equipment after proper disposal, read data from the data storage equipment, then send them out to client programs. This layer is composed of Business Objects (BO) such as JavaBean and session EJB. Client layer Presentation layer Request Bro wser JSP(Taglib) ActionForward Response <View> Data verificat ion Choose correct views ActionServlet (ActionMapping) fill request data ActionForm Mapping Action ActionForward <Control> pages data Business logic layer JavaBean EJB <Model> Hibernate Permanence layer Relational database Figure 3. Flow chart of the integration framework based on Struts and Hibernate Data Permanence Layer: This layer is composed of Hibernate that gains data from data source, then generates PO, and passes it to the business logic layer. In Hibernate, the Value Object(VO) acts as PO. Data Source Layer: The layer s another name is database layer, which stores the systematic application data. The entire system framework may be expressed by JSP-BO-DAO/VO(Hibernate)-DB[8]. The maximal characteristic of system frame is the combination 532

4 between presentation layer of Struts and data permanence layer of Hibernate. It adopts the multi-layer systematic structure to restrict the expression of application data within corresponding layers, which reduces data coupling among layers and improves the maintainability and expansibility of the overall framework. 5. Instance The realization of login system shows the flow of development the WEB application adopting by Struts and Hibernate framework. The system completes the input and checking of relevant messages including username and password. If the username input exists in the database and the password is correct, users can log on successfully. The other way round, users gets a frustrated result. 5.1 Application of Struts Framework Struts famework realizes the VC component of the Model-View-Controller design mode. (1)Jsp corresponds View component, and the HTML Taglib of Struts make Jsp become a pure View layer, the part codes of the login page are as follows: <html:form action="/login" method="post"> username : <html:text property="username"/> <html:errors property="username"/><br/> password : <html:password property="password"/> <html:errors property="password"/><br/> <html:submit/><html:cancel/> (2)ActionServlet corresponds Controller, transmits and controls by a configuration file of Strutsconfig.xml,whose part codes are as follows: <action attribute="loginform" input="/login.jsp" name="loginform" path="/login" scope="request" type="com.yourcompany.struts.action.loginaction"> <forward name="failed" path="/failed.jsp" /> <forward name="success" path="/success.jsp" /> </action> After ActionServlet receives the login request of user(login.jsp) according to the configuration file, the LoginForm that belongs to ActionForm class checks whether the username input exist in the database. The messages which LoginForm gets are past to LoginAction. LoginAction does with the operation transaction of checking the messages. (3)ActionForm pack up the form domain to become ActionForm object, which avoid the operations of get and set. ActionForm takes charge of collection messages. The statement of ActionForm(loginForm) in Struts-config.xml are as follows: <form-beans > <form-bean name="loginform" type="com.yourcompany.struts.form.loginform" /> </form-beans> 5.2 Application of Hibernate Framework The system creates Hibernate mapping while invoking Hibernate connection for the first time. At the same time the mapping file(user.hbm.xml) and the table object(user.java) are maked automatically. The User class is a POJO(Plain Old Java Object) which represent the user table of database. The properties of User mappings to the relational database by User.hbm.xml of configuration mapping-file. Every row of data in the relational database is a VO and every field in it is a property value. Hibernate mapping file explains the mapping relation of persistent classes and relational database tables, including of the relation of persistent classes. (1) The part codes of User.hbm. xml are as follows: <hibernate-mapping> <class name="org.jjyan.vo.user" table="user" catalog="database"> <id name="userid" type="java.lang.integer"> <column name="userid" /> <generator class="native" /> </id> <property name="username" type="java.lang.string"> <column name="username" length="20" notnull="true" /> </property> <property name="password" type="java.lang.string"> <column name="password" length="20" notnull="true" /> </property> </class> </hibernate-mapping> (2)Create an interface(iuserdao.java) to declare the methods of operating database,then adopt a java class(usermysqldao.java) inheriting the interface to realize the methods in order to operate the related table.here applying the inerface can easy to extend database.the codes of IUserDAO.java and UserMysqlDAO.java are as follows: (IUserDAO.java) public interface IUserDAO { public User ValidateUser(String username,string password); (UserMysqlDAO.java) public class UserMysqlDAO implements IUserDAO { 533

5 public User ValidateUser(String username, String password) { Session session = HibernateSessionFactory.getSession(); Query query = session.createquery("from User u where u.username=? and u.password=? "); query.setparameter(0,username); query.setparameter(1,password); User user=(user)query.uniqueresult(); return user; (3)Data transformation(operation logic transaction) between presentation layer and persistence layer is proceeded in Action which corresponds to Model layer and executes transaction logic. In Action the method of execute does many operations and returns ActionForward transmitted by controller. The action realizes the integration of Struts and Hibernate. The realization is as follows: public ActionForward execute(actionmapping mapping, ActionForm form,httpservletrequest request, HttpServletResponse response) { LoginForm loginform = (LoginForm) form; IUserDAO userdao = new UserMysqlDAO(); LoginForm lf = (LoginForm)form; String username=lf.getusername(); String password=lf.getpassword(); User user=userdao.validateuser(username, password); if(user!=null) { return mapping.findforward("success"); return mapping.findforward("failed"); 5.3 Advantages of the Integration In the login application, Struts realizes the complete division of View, Model and Controller, especially the labor of mend and maintenance of transaction is lighten by adopted configuration files. The system applies less SQL statements by Hibernate, such as the connection to database, search data and so on. So the development and maintenance of system become easier. design of applying Hibernate in Struts realizes the more effective framework of permanence layer. The integration of these two frameworks utilizes respective advantages fully to reach the consummate union as shown in the login system. Compare to writing SQL statements by hand, however, the fixed code generated by Hibernate when interacting with database lack of flexibility so developers can add SQL statements according to the need of systems. References [1] Hou Ting, The research and application of building Web application based on Struts and Hibernate,the Master's degree thesis of Wuhan University of Technology, Wuhan, April 2006, pp.6-7,9-11. [2]Xiong Ke, Design and Realization of Producing Management System on Basis of Struts and Hibernate, the Master's degree thesis of Sichuan University, Chengdu, April 2006, pp , [3] Wu Ming-hui, Wu Chao, Developing Web Application by Struts and Hibernate, Beijing: Posts & Telecom Press, Beijing, May [4] Hibernate Core for Java, 2008 [5] Gao Ang, Wei Wen-xue, Application of Java data persistence with Hiberna te and Struts framework, Computer Applications, Vol. 25 No. 12, Chengdu, Dec. 2005,pp [6] Ren Wenjuan, Wang hua, Ju Hongwei, Song Zhuqin, The Design and Implement of Web applications Based on Struts and Hibernate Framework, Microcomputer Information, Vol. 22 No. 9,Beijing,2006,pp [7]Liu Pan, Design and Reality of the Data-Operation Platform Based on Hibernate, the Master's degree thesis of Nanchang University, Nanchang, June 2005, pp [8] Zhao Qiang, Qiao Xin-liang, J2EE application development WebLogic JBuilder. Beijing: Electronic industry press, Summary In the entire system realization, Struts framework based on the MVC mode realizes layers partition of J2EE and solves code partition between the presentation layer and the business logic layer to realize code reuse. Hibernate can complete conversion between the relational database and the object model effectively. And it realizes the connection of objectoriented development and relational database. The 534