61, the life cycle of servlet
The web container loads servlet, and the life cycle begins. The initialization of the servlet is performed by calling the servlet's init () method. Different DO *** () methods are called depending on the request different by calling the service () method. End the service, the Web container calls the servlet's Destroy () method.
62, how to real real servlet single-thread mode
<% @ page isthreadsafe = "false"%>
63. Method of page object delivery
REQUEST, SESSION, Application, Cookie, etc.
64. What are the same and different from JSP and servlets, what is the connection between them?
JSP is an extension of servlet technology, essentially a simple way of servlet, and emphasizes the application's appearance expression. After JSP compiles "class servlet". The most important point of Servlet and JSP is that the application logic of servlet is in the Java file and is completely separated from the HTML in the representation. The case of JSP is that Java and HTML can be combined into a file that extension .jsp. JSP focuses on views, servlet is mainly used to control logic.
65, four session tracking technology
Session Scope Servlets JSP page description
Page No is a representative object and attribute related to a page. A page is represented by a compiled Java Servlet class (which can have any include instructions, but no include action). This includes both servlets and JSP pages compiled into a servlet.
Request is an object and attribute that represents a request issued to a web client. A request may span multiple pages, involving multiple web components (due to the relationship between the Forward Directive and the Include action)
Session is an object and attribute that represents a user experience with a web client. A web session can also request a number of client requests
Application is the object and attribute that represents the entire web application. This is essentially a global scope of the entire web application, including multiple pages, requests, and sessions.
66. The main method of the Request object:
SetAttribute (String Name, Object): Sets the parameter value of the request named name Name
GetaTtribute (String Name): Returns the value specified by name
GetAttributeNames (): Returns the name collection of all properties of the Request object, the result is an instance of an enumeration
getCookies (): Returns all Cookie objects of the client, the result is a cookie array
GetCharacterencoding (): Returns the character encoding method in the request
getContentLength (): Returns the length of the request
GetHeader: Get the file header information defined by the HTTP protocol
GetHeaders: Returns all values of the Request Header of the specified name, the result is an instance of an enumeration
GetHeadernames (): Returns the name of the Request Header, the result is an instance of an enumeration
GetInputStream (): Returns the requested input stream for obtaining the data in the request
GetMethod (): Get the method of transmitting data to server-side
GetParameter (String Name): Get the client to send to the server-side parameter value
getParameterNames (): Get the name of all the parameters of the client to the server side, the result is an enumerated instance getParameterValues (String Name): Get all the values of the parameters specified by Name
GetProtocol (): Get the name of the protocol that the client is transferred to the server.
getQueryString (): Get query strings
getRequesturi (): Get the client address that issues a request string
getRemoteAddr (): Get the IP address of the client
getRemotehost (): Get the name of the client
GetSession ([Boolean Create]): Return and request related session
GetServerName (): Get the name of the server
GetServletPath (): Get the path to the script file requested by the client
GetServerPort (): Get the port number of the server
Removettribute (String Name): Delete a property in the request
67. J2EE is a platform or a framework?
J2EE itself is a standard, a standard platform provided for the development of a distributed application.
J2EE is also a framework, including JDBC, JNDI, RMI, JMS, EJB, JTA and other technologies.
68. We often encounter some coded characters in the web application development process, such as ISO8859-1, how to output a certain coded string?
Public String Translate (String Str) {
String tempstr = ""
Try {
Tempstr = New String (Str.GetBytes ("ISO-8859-1"), "GBK");
Tempstr = tempstr.trim ();
}
Catch (Exception E) {
System.err.println (E.GetMessage ());
}
Return Tempstr;
}
69. Brief description of the difference between logic operation (&, |, ^) and conditional operation (&&, ||).
The difference between the two points: a. Condition operation can only be operated by Boolean, but logic operations can not only manipulate Boolean, but also operate value
b. Logic operations do not produce short circuits
70, how many forms of XML document definition? What is the essence difference between them? What kind of way to parse XML documents?
A: Two forms of DTD Schema, B: Essentially difference: Schema itself is XML, can be parsed by XML parser (this is also developing SCHEMA from DTD), C: There are DOM, SAX, Stax, etc.
DOM: It is very powerful when processing large files. This problem is caused by the tree structure of the DOM. This structure is more memory, and the DOM must load the entire document into memory before parsing the file. Suitable for random access to XML
SAX: Not present in DOM, SAX is an event-driven XML parsing method. It sequentially reads the XML file, and does not need to load all files all. When encountered at the beginning of the file, the end of the document, or the label is ended, it triggers an event, and the user handles the XML file by writing processing code in its callback event, suitable for the order of XML.
Stax: streaming API for XML (stax)
71, briefly describe the Similarities and As of Synchronized and java.util.concurrent.locks.lock?
Mainly identical: Lock can complete all the features implemented by SYNCHRONIZED
The main differences: LOCK has more accurate thread semanties and better performance than Synchronized. Synchronized will automatically release the lock, and LOCK must request the programmer manually to release and must be released in the finally clause. 72, EJB role and three objects
A complete EJB-based distributed computing structure consists of six roles, which can be provided by different developers, and every role must follow the EJB specification provided by Sun to ensure compatibility between each other. Sex. These six characters are EJB component developers, Application ASSEMBLERs, deployers, EJB server providers, EJB container providers (EJB container providers, System administrator
Three objects are Remote (local) interface, home (localhome) interface, Bean class
73, the service provided by EJB container
It mainly provides services such as declaration cycle management, code generation, continuous management, security, transaction management, lock and distribution management.
74. What are the prohibition of the prohibited operation in EJB?
1. Can't operate threads and threads API (thread API means NOTINE, WAIT, etc.) IO operation directly access file system, 6. You can't load local libraries.
75, the main role of the Remote interface and HOME interface
The Remote Interface defines a business method for the EJB client calling business method.
The HOME interface is an EJB factory for creating and removing a lookup EJB instance
76, lifecycle of bean instance
For Stateless Session Bean, Entity Bean, Message Driven Bean typically exists in cache management, which typically contains Cache management, set up the context, create EJB Object (create), business method call, remove, etc. Procedure, for the bean in which the buffer is managed, the instance is not removed from memory, but the buffer pool scheduling mechanism continues to reuse the instance, and the bean in which Cache Management is used, the BEAN is maintained by activating and deactivating the mechanism. Limit the number of instances in memory.
77, EJB activation mechanism
Take Stateful Session Bean as an example: The Cache size determines the number of bean instances that can exist in memory. According to the MRU or NRU algorithm, instance is migrated between activation and deactivation, and the activation mechanism is when the client calls an EJB. When an instance business method, if the corresponding EJB Object discovers that it does not bind the corresponding bean instance, the reactive bean storage (by serializing mechanism storage instance) is replied (activated) this instance. The corresponding EJBACTIVE and EJBPASSIVATE methods are called before the state change.
Several types of 78, EJB
Session Bean, entity (Entity) bean message driver (Message Driven) bean
Session bean can be divided into stateful and stateless, two entity beans can be divided into two kinds of sustainability (BMP) and container management of BEAN management (CMP).
79. Several basic steps for customer service calls EJB objects
Set the JNDI service factory and the JNDI service address system property, find the Home interface, call the CREATE method from the Home interface to create a Remote interface, and call its business method through the Remote interface.
80, how to specify the size of the size to WebLogic?
In the Script of WebLogic (bitservername in the Domian corresponding server directory), add SET MEM_ARGS = -XMS32M -XMX200M, adjust the minimum memory to 32M, maximum 200M
81. How to set the hot start mode (development mode) of WebLogic and product release mode?
The startup mode of the corresponding server can be modified in the management console is one of the development or product modes. Or modify the service startup file or Comufact of the Commenv file, add set production_mode = true.
82. Do you need to enter your username and password when starting?
Modify the service launch file, add WLS_USER and WLS_PW items. You can also add an encrypted username and password in the boot.properties file.
83. After the application domain (or a website, Domain) is configured to configure the relevant information such as a application domain (or a website, domain) in the WebLogic Management State, which is actually saved in what file?
Save in the config.xml file of this Domain, it is the core profile of the server.
84, talk about a Domain default directory structure in WebLogic? For example, put a simple helloworld.jsp into the point of the directory, but you can be http: // host on the browser: port number // HelloWord .jsp You can see the result of the running?
Domain Directory / Server Directory / Applications, place the application directory in this directory will be available as an application access. If it is a web application, the application directory needs to meet the web application directory requirements, the JSP file can be placed directly in the application directory, Javabean needs to be put In the CLASSES directory for the application directory, the default application that sets the server will be able to implement the application name on your browser.
85. What configuration files need to be involved in the WEBLOGIC?
The configuration files involved in different types of EJBs have different configuration files including EJB-jar.xml, weblogic-ejb-jar.xmlcmp entity beans generally need WebLogic-Cmp-Rdbms-jar.xml
86. How to make an SSL configuration in WebLogic to configure the client's authentication configuration or talk about J2EE (standard) for SSL configuration
Using DemoIdentity.jks and Demotrust.jks KeyStore in the default installation, you need to configure the server to use Enable SSL, configure its port, you need to get private key and digital certificate from CA in product mode, create Identity and Trust KeyStore, load get Keys and digital certificates. You can configure this SSL connection to one-way or two-way.
87. How to view EJBs already released in WebLogic?
You can use the management console, you can view all published EJBs in its deployment
88, what is CORBA? What is the use?
The CORBA standard is a common object request agency structure, which is standardized by object management organization (Object Management Group, abbreviated as OMG). Its composition is the interface definition language (IDL), language binding (binding: also translated into a cable) and an agreement to interoperate interoperability. Its purpose is to use different programming languages to run in different processes, develop in different operating systems. 89. Talk about several common modes in J2EE you are familiar or have heard? And some views on design patterns
Session Facade Pattern: Accessing EntityBean using sessionbean
Message Facade Pattern: Realization asynchronous call
EJB Command Pattern: Use Command JavaBeans to replace sessionBean to achieve lightweight access
Data Transfer Object Factory: Simplify EntityBean Data Provision for DTO Factory
Generic Attribute Access: Simplify EntityBean Data Provision for EntityBeaN
Business Interface: Realize the same interface to specify business logic through remote (local) interface and bean classes
The design of the EJB architecture will directly affect the performance, scalability, maintenanceability, components reusability and development efficiency. The more complex the project, the more important the project team, the more important it can reflect the importance of good design.
90, tell the difference between Persistent and Non-Persisten when developing message beans in WebLogic
The MDB of the Persistent method ensures the reliability of the message delivery, that is, if the EJB container has problems, the JMS server will send the message when this MDB can be used, and the Non-Persistent method will be discarded.
91. What kind of method is generally implemented when the servlet is executed?
Public void init (servletconfig config)
Public servletconfig getServletConfig ()
Public String GetServletInfo ()
Public void service (servletRequest Request, ServletResponse Response)
Public void destroy ()
92, J2EE common design model? Description plant mode.
23 design patterns in Java:
Factory, Builder, Factory Method (factory method mode),
Prototype, Singleton, Facade (facade),
Adapter, Bridge (Bridge mode), Composite (synthesized mode),
Decorator, Flyweight, Proxy (proxy mode),
Command, Interpreter, Visitor (Visitor Mode), Iterator, Mediator, MEMENTO (Memo Mode),
Observer (Observer mode), Strategy, Strategy (Policy),
Template Method (Template Mode), Chain of Responsibleity (Responsibility Chain Mode)
Factory mode: Factory mode is a model that is often used. The class implemented according to the factory mode can generate an instance of a class in a set of classes in accordance with the data provided. Usually this set of categories have a public abstract parent class and The same method is achieved, but these methods have different operations for different data. First, you need to define a base class that the subclass of the class implements the method in the base class through a different method. Then need to define a factory class, and the factory class can generate different subclass examples depending on the conditions. When an example of a subclass is obtained, the developer can call the method in the base class without having to consider the instance of which a subclass is returned.
93, EJB needs to implement its business interface or home interface, please briefly describe the reasons.
The remote interface and home interface do not need to be directly implemented, and their implementation code is generated by the server, and the implementation class in the program run is used as an instance of the corresponding interface type.
94. What kinds of methods are there? Please list it. Implement a rapid sort with Java.
Sort by: Insert Sort (Direct Insert, Hill Sort), Switching Sort (Bubble Sort, Rapid Sort), Select Sort (Direct Selection Sort, Stack Sort), Multiple Sort, Distribution Sort (Sort, Base Sort )
Quickly sorted pseudo code.
/ / Sort a Quick Sorting Method to A [0: N- 1]
Select an element from a [0: N- 1] as M i D l E, the element is fulfilled
The remaining elements are divided into two LEFTs and R I g h t, so that the elements in L E f T are less than or equal to the fulcrum, and the elements in the RIGHT are greater than equal to the fulcrum
Returning use of fast sorting methods to sort Left
Returning use of rapid sorting methods to sort Right
The result of the result is L E f T M I D D L E R I g H t
95, explain the following noun commonly used in J2EE (or briefly description)
Web container: Provides an environment to the application component (JSP, servlet) that interacts the JSP, Servlet directly more in the container, and does not have to pay attention to other system issues. There is mainly a web server to achieve. For example: Tomcat, WebLogic, WebSphere, etc. The interface provided by the container strictly abides by the Web Application standard in the J2EE specification. We call the Web Server of the above standards called the web container in J2EE.
EJB container: Enterprise Java Bean container. More industry segments. He provides various management functions that run the component EJB. As long as the EJB that satisfies the J2EE specification is placed in this container, it will be managed by the container. And you can obtain system level services through ready-made interfaces. For example, email services, transaction management.
JNDI: (Java Naming & Directory Interface) Java Name Directory Service. The main functionality is: Provide a directory system that allows applications from all over its own index to meet the functionality of fast finding and positioning distributed applications. JMS: (Java Message Service) Java Message Service. It mainly implements communication between the various applications. Includes point-to-point and broadcast.
JTA: (Java Transaction API) Java Transaction Services. Provide a variety of distributed transaction services. The application only needs to call the interface provided.
JAF: (Java Action Framework) Java Security Authentication Framework. Provide some security control frames. Let developers implement their own personal safety control strategies through a variety of deployment and customization.
RMI / IIOP: (Remote Method Invocation / Internet Object Request a Intermediary Protocol) They are primarily used to serve through remote calls. For example, remotely running a program, which provides stock analysis services, we can implement them directly on your local computer. Of course, this is to communicate between heterogeneous systems through a certain specification. RMI is unique to Java.
96. How does Java language processes an exception handle, keywords: throws, throw, try, catch, finally represents what significance? Can I throw an exception in the TRY block?
Java processes abnormally by object-oriented methods, and classifies a variety of different exceptions and provides a good interface. In Java, each exception is an object, which is an instance of the throwable class or other subclass. When an abnormality occurs, an exception object is thrown, and the object contains abnormal information, and the method of calling this object can be captured and processed. Java's exception handling is achieved by 5 keywords: try, catch, throw, throws and finally. Under normal circumstances, use TRY to perform a program, if an exception occurs, the system will throw an exception, then you can capture (catch) it through its type, or finally by default processor Treatment.
Use TRY to specify a program that prevents all "exceptions". Keeping followed by the Try program, a Catch clause should be included to specify the type of "exception" you want to capture.
The throw statement is used to clearly throw an "exception".
Throws is used to indicate a variety of "exceptions" that may be thrown by a member function.
Finally is executed to ensure that "exception" occurs regardless of the code.
You can write a TRY statement outside in a member function call, write another TRY statement to protect other code inside this member function. Whenever you encounter a try statement, the "exception" frame is placed on the stack until all TRY sentences are completed. If the TRY statement at the next level does not process some "exception", the stack will be expanded until the TRY sentence with this "exception" is encountered.
97, can I include multiple classes (not internal classes) in a ".java" source file? What is the limit?
can. There must be only one class name with the file name.
98, all parts of MVC have those technologies to achieve? How to achieve?
MVC is a short written by Model-View-Controller. "Model" is the application's business logic (implemented by javabean, ejb component), "view" is the application's representation surface (generated by JSP page), "Controller" is a process control (generally a servlet) The application logic, processing procedure, and display logic are achieved by this design model into different components. These components can interact and reuse. 99. How many ways to implement a thread in Java? What is the use of keyword modified synchronization methods? Stop () and SUSPEND () methods do not recommend it?
There are two implementation methods, which are inherited the Thread class and the implementation of the runnable interface.
Synchronization method with synchronized keyword
Oppose the use of STOP () because it is not safe. It will release all locks acquired by the thread, and if the object is in a non-connected state, then other threads can check and modify them in that state. It is difficult to check the real problem. The suspend () method is prone to dead locks. When you call suspend (), the target thread will stop, but still hold the lock before this. At this point, any other thread cannot access the locked resource unless the thread is restored to the thread. For any thread, if they want to resume the target thread, it will cause a deadlock to use any lock resources. So you should not use Suspend (), and you should place a sign in your own Thread class, pointing out that the thread should act or hang. If the flag indicates that the thread should hang, use Wait () to enter the waiting state. If the flag indicates that the thread should be restored, use a Notify () to restart the thread.
100. How many types of streams in Java? JDK provides some abstract classes for each type of stream for inheritance, please say which classes are they?
Byte stream, character stream. Byte streams are inherited in InputStream / OutputStream, and the character stream is inherited in InputStreamWriter. There are many other streams in Java.IO bag, mainly in improving performance and convenience.
101. Does memory leaks in Java? Please briefly describe it.
meeting. Such as: INT I, I2; RETURN (I-I2); // when i is a positive number, i2 is a large negative number. The result will cause a seating, resulting in errors.
102. What is the mechanism for achieving polymorphism in Java?
The method of rewriting Overriding and overloading overloading is a different manifestation of Java polymorphism. Overriding Overriding is a manifestation of polymorphism between parent class and subclasses, and overloading overloading is a manifestation in a class.
103. What is the basic principle of garbage collector? Can garbage collectors recycle memory immediately? Is there any way to actively notify the virtual machine for garbage collection?
For GC, when the programmer creates an object, the GC starts to monitor the address, size, and usage of this object. Typically, the GC uses a map-like manner to record all objects in the heap (HEAP). In this way, it is determined which object is "can be reached", which object is "unreachable". When the GC determines that some objects are "unreachable", GC is responsible for reclaiming these memory spaces. can. The programmer can manually execute System.gc (), inform GC operation, but Java language specification does not guarantee that GC will be executed.
104, differences in static variables and instance variables?
STATIC i = 10; // constant
Class a a; a.i = 10; // variable 105, what is Java serialization, how to implement Java serialization?
Serialization is a mechanism for processing the target stream, the so-called object stream is to fluidize the contents of the object. It is possible to read and write the fluidized object, and the flowable object can also be transmitted between the network. Serialization is to solve problems caused by read and write operations on object flows.
Serialization Realization: The sequential class is required to implement the serializable interface. The interface does not need to be implemented. Implements Serializable is only serialized in order to mark the object, and then use an output stream (such as a fileoutputstream) to construct An ObjectOutputStream (Object Stream) Object, then use the ObjectOutputStream object's WriteObject (Object Obj) method to write the objects of the object (ie, save its status), if you want to recover, you can use the input stream.
106. Can I send a call to a non-Static method from one STITIC method?
No, if it contains Method () of the object; cannot guarantee the initialization of the object.
107, when writing clone () methods, there is usually a line of code, what is it?
Clone has default behaviors, super.clone (); he is responsible for generating the right size space and copying in position.
108, in Java, how to jump out the current multi-nest loop?
Use Break; Return method.
109, List, Map, SET three interfaces, how is it?
List holds an element in a specific order, there can be repeated elements. SET cannot have a repeating element, internally sorted. Map saves the key-value value, Value can be more values.
110, what is J2EE?
J2EE is a Multi-Diered, distributed, distributed, component-based, enterprise application model. In such an application system, it can be divided according to functionality. For different components, these components can be on different computers and are in the corresponding hierarchy (TIER). The hierarchies are included in the ClientN Tier components, web layers, and components, Business layers, and components, and corporate information systems (EIS) layers.
111, UML
Standard Modeling Language UML. Modal example, static map (including class diagram, object map, and package), behavioral diagram, interaction map (sequential diagram, cooperation graph), implementation diagram.
112, say some common class, package, interface, please give 5
Common class: BufferedReader BufferedWriter FileReader Filewirter String Integer
Common package: java.lang java.awt java.io java.util java.sql
Common interface: Remote List Map Document NodeList
113. In the development, the design model is used? What is used?
Each mode describes a problem that has emerged in our environment and then describes the core of the solution. In this way, you can use the existing solutions countlessly without counting the same job. Mainly used in the design pattern of MVC. Used to develop JSP / Servlet or J2EE related applications. Simple factory model, etc.
114, what actions do you have? What is the role?
JSP has the following six basic action JSP: include: Introducing a file when the page is requested. JSP: Usebean: Find or instantiate a JavaBean. JSP: setProperty: Sets the properties of JavaBean. JSP: getProperty: Outputs the properties of a JavaBean. JSP: Forward: Turn the request to a new page. JSP: Plugin: Generate Object or Embed tags based on the browser type. 115, Anonymous Inner Class (anonymous internal class) Can IMPLEMENTS INTERFACE?
You can inherit other classes or complete other interfaces, this way is commonly used in Swing program.
116. The difference between application servers and web Server?
Application Server: WebLogic, Tomcat, JBoss
Web Server: IIS, Apache
117, the connection and difference between BS and CS.
C / S is the abbreviation of Client / Server. Servers typically use high-performance PCs, workstations, or small machines, and use large database systems such as Oracle, Sybase, Informix, or SQL Server. The client needs to install a dedicated client software.
B / S is an abbreviation of Brower / Server, just install a browser, such as Netscape Navigator or Internet Explorer, such as Netscape Navigator, or Internet Explorer, and a database such as Oracle, Sybase, Informix, or SQL Server. In this configuration, the user interface is implemented completely through the WWW browser, and the transaction logic is implemented at the front end, but the main transaction logic is implemented at the server. The browser interacts with the database with the database.
C / S and B / S difference:
1. The hardware environment is different:
C / S is typically built on a dedicated network, a small network environment in a small area, and the local area network provides connection and data exchange services through a dedicated server.
B / S is built on the WAN, which is not necessarily a special network hardware environment, examples of online Internet access, renting equipment. Information yourself, there is a stronger adaptation range than C / S, usually as long as there is operating system and browser
2. Different security requirements
C / S typically facing relatively fixed user groups, which is very controlled for information security. Generally high confidential information systems are suitable for C / S structures. Open information can be publicly available via the B / S distribution section.
B / S is built on a wide area network, which is relatively weak for security control capabilities, and may facing unknown users.
3. Different program architectures
The C / S program can be more focusing on the process, and you can check the permissions multi-level check, which can be considered less.
B / S has a multiple consideration of security and access speed, based on the more optimized basis. The program architecture of the B / S structure B / S structure is a trend of development, from the MS .NET series BizTalk 2000 Exchange 2000, etc., fully supporting the system for network components. SUN and IBM push JavaBean component techniques, etc., make B / S mature more mature.
4. Software is reused
The C / S program can be inevitable integrally, the reuse of the component is not as low as the reuse of the components of B / S.
The multi-structure of B / S is required to relatively independently. It is relatively good to be reused. If the table buying table can be used, not the stone table on the wall
5. System maintenance
Due to overall performance, the C / S program must be overall, the problematic problems and system upgrades. Upgrade is difficult. Maybe a new system
The B / S component consists of individual replacement, realizing seamless upgrading of the system. The system maintenance cost is minimized. Users can download and install themselves from the Internet.
6. Different problems
The C / S program can handle the user plane, and high demand in the same area, security requirements, related to the operating system. It should be the same system B / S is built on wide area network, facing different user groups, dispersing the region, this is C / S cannot be done. The relationship with the operating system platform is the smallest.
7. Different user interface
C / S is mostly established Window platform, the performance method is limited, and the programmer is generally required.
B / S is built on a browser, there is a richer and vivid way to communicate with the user. And most difficulty is reduced, and the development cost is reduced.
8. Different information flow
The C / S program is generally a typical centralized mechanical treatment, relatively low interactivity.
B / S information flows to change, B-B B-C B-G and other information, the flow direction changes, more like the trading center.
118, Linux under the thread, the explanation of the GDI class.
Linux implemented is based on the "one-to-one" thread model of the core lightweight process, and a thread entity corresponds to a core lightweight process, and the management between the thread is implemented in the nuclear external function library.
The GDI class is an image device programming interface class library.
119, Struts application (such as Struts architecture)
Struts is an open source of the open source of the web application using Java Servlet / JavaServer Pages technology. The Struts can develop an application architecture based on MODEL-View-Controller design mode. Struts has the following main functions: I contain a controller servlet to send the user's request to the corresponding Action object. II.Jsp Free Tag Library and provide association support in the Controller Servlet to help developers create interactive form applications. 3. Provide a series of practical objects: XML processing, automatically handle JavaBeans properties, international tips and messages through Java Reflection APIs.
120, what is JDO?
JDO is a new norm of Java object persistence, which is a referred to as Java Data Object, and is also a standardized API for accessing objects in some data warehouse. JDO provides transparent object storage, so that the developer does not require additional code (such as the JDBC API). These cumbersome routines have been transferred to the JDO product provider, so that developers are freed out to concentrate on time and energy logically. In addition, JDO is flexible because it can run on any data underlayer. JDBC is just more common to relational database (RDBMS) JDO, providing storage capabilities of any data underlying, such as relational database, file, xml, and object database (ODBMS), etc., make it stronger to apply portability.
