CN100595732C - A Method of Obtaining Class Loading Information in Application Server - Google Patents

Abstract

The present invention provides a method for obtaining class loading information in an application server, comprising: registering a listener with the class loader when the application server is started; and activating the registered listener when the application server is running and instantiating the class loader listener; the listener accepts the trigger and responds to the trigger; the listener saves the class loader instance reference, and can obtain the internal class loading information of the application server through a simple client/local call, reducing Reduce the workload of troubleshooting and debugging, and reduce the maintenance cost of the application server.

Description

A Method of Obtaining Class Loading Information in Application Server

technical field

The invention relates to the field of application servers, in particular to a method for acquiring class loading information in the application server.

Background technique

At present, in the Internet/Intranet/Extranet environment, most enterprise-level application systems adopt three-tier or multi-tier application modes. In order to facilitate the development, deployment, operation and management of applications based on multi-layer structure, it is necessary to build a complete application framework based on the underlying technology of network and distributed computing, and provide corresponding supporting platforms as the infrastructure of multi-layer applications. The key to supporting the platform is the application server in the middle layer. Application server is a platform for creating, deploying, running, integrating and maintaining multi-tier distributed enterprise applications. In enterprise applications, application servers can provide the following benefits: improve the effectiveness of enterprise application development, ensure the reusability of business logic and components; improve the performance of enterprise applications, such as high operating performance and response time, scalability, reliability, etc. ; Make enterprise applications easier to monitor and manage, reducing system maintenance and upgrade costs. Due to the important role and key position of the application server, it has become a hot spot in the industry today.

Class loading is one of the most powerful mechanisms provided by the Java language. A class represents the code to be executed, and data represents its related state. State changes all the time, code doesn't. When we associate a specific state with a class, it means instantiating a class. Although the states of instances corresponding to the same class vary widely, they essentially all correspond to the same piece of code. Once a class is loaded into the Java Virtual Machine (Java Virtual Machine, JVM), the same class will not be loaded again. The startup of the application server itself needs to load many class files, and the application deployed on the application server also needs to load the class files of the application itself when starting. The class loading mechanism of JAVA is to load class files in the same JVM according to the level and order of the class path, and the same class loader (classloader) can only load the same class once, classloader has a parent-child relationship, the same class file It can be loaded by different classloaders, and a class can be loaded by multiple class-loaders.

When the application server is running, a certain class of the application may be deployed in multiple places. During the development and production process, application developers often need to obtain information about the class loaded by the classloader for the purpose of troubleshooting and debugging. . For example, obtain the physical location of the class file corresponding to this class, which classloader loads this class file, and so on.

There are several methods for obtaining such information in the prior art as follows:

1. Output the required information in the application code through hard coding, that is, after finding an error, modify the application code and add a piece of code. After starting, you can see the physical location of the specific class file on the console or load the classloader for class files. Outputting in the hard-coded manner requires modification of the code, and increases the output of garbage logs, resulting in a decrease in application performance.

2. Output the required information through third-party software, such as using third-party software such as jprofile. The reason why the third-party software can analyze the information of threads and class loading in the JVM is that the entire application server process must be hosted For the third-party software, the third-party software specifically maintains the life cycle of the entire application server process, so the configuration is very complicated, and the third-party software is commercial software, which needs to be purchased, and the economic cost is high.

3. By writing the JMX function module and embedding it in the application to output the required information, the development of the JMX component is very large and the complexity is very high.

From the above analysis, it can be seen that the above three methods all require a lot of work by the development and maintenance personnel, and the cost is high, and no matter which method is adopted, the corresponding information cannot be obtained in time in the wrong application environment, and this One point is very important for application debugging. Therefore, there is an urgent need for an information acquisition method that is simple, economical, and capable of obtaining application error information in a timely manner.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for obtaining class loading information through a simple client/local call.

In order to solve the above problems, the present invention discloses a method for obtaining class loading information in an application server, including:

Register the listener with the class loader;

when the class loader is instantiated, activate said registered listener;

the listener accepts a trigger and responds to the trigger;

The listener holds a class loader instance reference.

The specific steps of the registration listener include:

Implement an Mbean class loader monitoring service that complies with the Java EE specification;

Configuring the class loader monitoring service in the startup service list of the application server;

Register listeners with the class loader monitoring service.

The concrete process of described preservation is:

The listener saves the class loader instance reference in a data structure in memory.

Further, it also includes:

Receive a local/client request, and output the saved class loading information.

Preferably, the step of outputting class loading information specifically includes:

Call the class loader monitoring service locally;

The class loader monitors the service response, accesses and returns saved class information through the saved class loader.

Preferably, the specific steps of outputting class loading information include:

The client logs in to the application server;

Initialize the JMX connector;

Obtain the service management component Mbean interface of the specified service name;

The information is obtained by calling the interface.

Preferably, the specific steps of outputting class loading information include:

The client/local invokes the Mbean interface of the service management component of the class loader monitoring service to request the number of class loader instances in the application server;

The class loader monitors the service response, returning the number of saved class loader instances.

Preferably, the step of outputting the class loading information specifically includes:

a1. The client/local invokes the Mbean interface of the service management component of the class loader monitoring service;

a2. The class loader monitors the service response;

a3. Determine whether a specific class loader instance is specified in the specified interface call, if not specified, enter step a4;

a4. Traverse all saved class loader instances;

a5. Determine whether the class loader instance has loaded the class with the given class name, otherwise return to step a4, and if yes, enter step a6;

a6. Constructing a class information value object, said class information value object including the class loader for loading the class, and the physical path of the class file;

a7. Return the class information value object.

Preferably, the step of outputting the class loading information specifically includes:

b1. The client/local invokes the Mbean interface of the service management component of the class loader monitoring service;

b2. The class loader monitors the service response;

b3. Determine whether a specific class loader instance is specified in the specified interface call, and if not specified, enter step b4;

b4. Traverse all saved class loader instances;

b5. Determine whether the class loader instance has loaded the class with the given class name, otherwise return to step b4, and if yes, enter step b6;

b6, constructing the class information value object, the class information value object including the class loader for loading the class, the physical path of the class file, adding the class information value object into the class information value object collection;

b7, judging whether there is a class loader instance, if yes, return to step b4, otherwise enter step b8;

b8. Return the class information value object set.

Preferably, the step of outputting the class loading information specifically includes:

c1, the client/local calls the service management component Mbean interface of the class loader monitoring service;

c2. The class loader monitors the service response;

c3. Determine whether a specific class loader instance is specified in the specified interface call, and if so, enter step c4;

c4. Determine whether the specified class loader instance has loaded the class with the given class name, otherwise return a null value, and if so, enter step c5;

c5. Constructing a class information value object, said class information value object including the class loader for loading the class, and the physical path of the class file;

c6. Return the class information value object.

Compared with the prior art, the present invention has the following advantages:

The present invention registers the listener with the class loader when the application server is started, activates the registered listener when the class loader is instantiated, and saves the instance reference of the class loader after the listener responds. When the application server is running, through a simple client/local call, you can obtain the class loading information such as the information about the java class with the given class name being loaded by the classloader and the physical location of the corresponding class file. Obtaining class loading information through the present invention does not require additional configuration and coding by application developers and maintenance personnel, and does not affect performance. The internal class loading information of the application server can be obtained through simple client/local calls, reducing troubleshooting, Reduce the workload of debugging and reduce the maintenance cost of the application server.

Description of drawings

Fig. 1 is a flow chart of a method for obtaining class loading information in an application server according to the present invention;

Fig. 2 is a flow chart of a method for obtaining class loading information in an application server according to the present invention;

Fig. 3 is another kind of flow chart of the method for obtaining class loading information in the server of the present invention;

Fig. 4 is a flow chart of a method for obtaining the number of class loader instances in the present invention;

Fig. 5 is a flow chart of a method of obtaining class loading information when a class with a given class name is loaded according to the present invention;

Fig. 6 is another method flowchart of the present invention to obtain class loading information when a class with a given class name is loaded;

Fig. 7 is a flowchart of a method for obtaining class loading information of a specified class name loaded in a specified class loader according to the present invention.

Detailed ways

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

As a solution for enterprise-level applications, the application server should provide: (1) the ability to speed up the development process, ensure the development quality, and promote the application to enter the market quickly; (2) the deployment ability to enable the application to run in a flexible and effective manner; ( 3) Integration ability to effectively integrate with various back-end systems. The flexibility and functions needed to help customers build, deploy and run enterprise applications come from the combination and use of various capabilities of application servers. Specifically, the functions of the application server can be divided into core services and extended services. Core services: provide support for the realization of business logic; manage the application server; provide an engine for protocols and interfaces, support communication protocols (such as HTTP, IIOP), database interconnection standards (such as JDBC, ODBC), distributed computing protocols, etc. Various industry standards. Extended service: functions that should be provided to support high-end applications, mainly including: transaction processing, cluster, fail over, load balancing, cache mechanism, security service, and enterprise existing It has the integration ability and development effectiveness of the application system (the ability to combine with the application development environment and tools).

The most significant development in application server technology in recent years is the emergence of J2EE (Java 2 Platform Enterprise Edition). J2EE is a standard platform for developing, deploying, running and managing Java-based distributed applications proposed by Sun. It is based on the Java 2 Platform Standard Edition (J2SE), inherits many advantages of the standard edition, and also provides comprehensive support for technologies such as EJB, Java Servlet, and JSP. J2EE uses EJB Server as the deployment environment for commercial components, and provides services required by components in a distributed computing environment in EJB Server, such as component lifecycle management, database connection management, distributed transaction support, component naming services, etc. .

J2EE has its advantages in implementing application servers. It can provide a complete underlying framework for the implementation of application servers by utilizing the performance of Java language itself in terms of cross-platform, portability, object characteristics, and memory management. Various services defined in J2EE, including JSP and Servlet containers, EJB containers, JDBC, JNDI (name directory service), JTS/JTA (transaction service), JMS (message service), etc., also provide various services for application servers. support. EJB components that implement business logic can run more efficiently in application servers. Users can call EJBs running in EJB Server through Java Servlet or JSP, and can also directly access components running in EJB Server through IIOP. In addition to the basic features of the application server, the J2EE application server should also implement: support industry standards for Java programming, including EJB, JDBC, JNDI, RMI-IIOP, JCA, JTS/JTA, etc.; , VisualCafe, etc.) integration; compatible with standard Java operating platforms, such as Sun, IBM and other system platforms; using complete Java language coding to ensure good portability and support Java language features.

The class loading of the Java virtual machine (JVM) is to load the bytecode contained in the class file into the JVM, but the class loader is not loaded into the JVM intact, it is the class (.class) file The content is converted into class bytecode used by the JVM. The bytecode data loaded into the JVM through the class loader becomes executable code. The class loader loads the class into the JVM through three steps: loading, linking, and initialization.

The class loader itself is also a java class, and the class library provides a java.lang.classloader as the base class of the class loader, which means that the real class loader must be a subclass of classloader. A getclassloader method is defined in the Class class, which is used to return the class loader object of the class it describes, and the type of the returned object is classloader. A java application continues to use two types of class loaders: the root loader (bootstrap) and the user-defined loader (user-defined). The so-called root loader is a class embedded in the JVM, which uses specific operations The native code of the system is implemented, and it does not need a special class loader to load. It is responsible for loading the classes in the class files in the java core package. For a class that has been loaded by the parent class loader. By default, the JVM also uses this parent class loader to load other classes it calls. Since the parent class loader will not entrust the child class loader to load classes, in general, a parent class Classes loaded by a loader cannot call other classes that can only be discovered and loaded by child class loaders.

The present invention is by realizing a class loader monitoring service (clservice) that conforms to the Java EE Mbean norm, and described clservice provides three interfaces, and described each interface can realize following function: (1) obtain the classloader example number in the server; (2) ) Obtain the information that a class with a given class name is loaded; (3) Obtain the information that the specified class name is loaded in the specified classloader. The class loader monitoring service is configured in the startup service list of the application server, and the listener (listener) is registered through the class loader monitoring service. Except the system classloader instance, each classloader running in the application server process is in the When instantiated, the registered listener will be triggered and the classloader reference will be saved. When the application server is running, through a simple client/local call, you can obtain the class loading information such as the information about the java class with the given class name being loaded by the classloader and the physical location of the corresponding class file. Obtaining class loading information through the method described in the present invention does not require additional configuration and extra coding by development and maintenance personnel, and does not affect performance. The internal class loading information of the application server can be obtained through simple client/local calls, reducing the number of queues. The workload of error and debugging is reduced, and the maintenance cost of the application server is reduced.

Referring to Fig. 1, it shows a flow chart of a method for obtaining class loading information in an application server according to the present invention, including:

Step 101, register a listener.

To realize the present invention, it is first necessary to add a new mechanism in the application server, adding a class loader (classloader) initialization event trigger-response mechanism. The mechanism is that, in addition to the system classloader instance, when each classloader running in the application server process is instantiated, a classloader initialization event (hereinafter referred to as cievent) will be triggered. The cievent itself is a JavaBean object, which contains the The initialized classloader instance. Secondly, it is necessary to implement a classloader monitoring service (hereinafter referred to as clservice) that conforms to the JavaEE Mbean specification. And the service is configured in the startup list of the application server, and a listener (listener) is registered through the class loading monitoring service (clservice). The clservice provides three interfaces, namely: 1) public ClassDesc[] findClass(String className), to obtain the class description information of the specified class name, the same class name may exist in different classloaders; 2) public ClassDesc findClass (String className, ClassLoader baseCL), specifies the classLoader to obtain class information; 3) public intgetClassLoaderCount(), obtains the instance number of the classloader in the current JVM, and the interface can be called by the client through local or remote calls. It can be known from the above description that each interface can realize the following functions: (1) obtain the number of classloader instances in the server; (2) obtain the loaded information of a class with a given class name; (3) obtain the specified class Name information loaded in the specified classloader.

Step 102, activate the registered listener.

The registered listener is activated when the application server is running and the class loader is instantiated. In addition to the system classloader instance, when each classloader running in the application server is instantiated, the classloader initialization event (cievent) will be triggered, and the event will be accepted by the registered listener (cilistener), that is, activate the registered listener.

Step 103, the listener accepts the trigger and responds.

The registered listener can receive the triggered classloader initialization event and make a response.

Step 104, save the classloader instance reference.

The class loader initialization listener (cilistener) obtains the ClassLoader instance from the class loader initialization event (cievent), and saves it in the data structure of the memory. Instance reference is a vocabulary in Java. After a class is instantiated, an instance reference to the class will be generated.

Further, step 105 is also included, receiving a client/local request, and outputting saved class loading information.

In step 104, the listener saves the class loader instance reference in its own data structure, and outputs the saved class loading information after receiving a local/client output request for class loading information.

Referring to FIG. 2, it shows a flow chart of a method for an application to obtain class loading information in a server according to the present invention, including:

Step 201, call the class loader monitoring service locally.

Call the Mbean interface of clservice locally, and send a request to the application server to obtain class loading information.

Step 202, the class loader monitors the service response and returns the class loading information.

The clservice in the application server responds to the request, accesses and returns the saved class loading information through the saved class loader.

The method shown in FIG. 2 is based on local calls and local requests to obtain class loading information. The local means that the client and the application server run in the same java virtual machine (JVM). The calling method is as follows:

ClassLoaderServiceMBean service＝(ClassLoaderService)Config.getService(ClassLoaderService.OBJECT_NAME), to obtain a class loader monitoring service, you can directly pass:

service. getClassLoaderCount();

service.findClass(class name);

service.findClass (class name, ClassLoader instance) access to obtain class loading information.

Referring to FIG. 3 , it shows a flow chart of another method for obtaining class loading information in an application server according to the present invention, including:

Step 301, the client logs in to the application server.

The method shown in FIG. 3 is based on remote invocation, and the remote client requests to obtain the class loading information of the application server. The remote means that the client and the application server are not in the same JVM.

Step 302, initialize the JMX connector;

JMX (Java Management Extensions) is a framework for embedding management functions into applications. JMX is a set of standard agents and services. In fact, users can use these agents and services to implement management in any java application. The JMX system is divided into three layers: a, presentation layer; b, agent layer; c, distributed service layer.

Step 303, obtaining the Mbean interface of the specified service name;

Step 304, obtain information through the interface call.

The calls shown in the method in Figure 3 are all in compliance with the JMX specification. In these calls, in addition to the part that meets the specification, some configuration information needs to be specified: (1) the path of the jaas authentication file for logging in to the application server; (2) the path for logging in to the application server User name/password of application server; (3) address of application server, adopt iiop agreement in java; (4) given Mbean name, obtain Mbean; (5) provide the class name of the class that will obtain class loading information.

Referring to FIG. 4 , it shows a flowchart of a method for obtaining the number of class loader instances of the present invention, including local acquisition and client remote acquisition, including:

Step 401, the client/local invokes the Mbean interface of the class loader monitoring service, and requests to obtain the number of class loader instances in the application server.

Step 402, the class loader monitors the service response, and returns the number of saved class loader instances.

Referring to FIG. 5 , it shows a flowchart of a method for obtaining class loading information when a class with a given class name is loaded according to the present invention, including:

Step 501 , the client/local invokes the Mbean interface of the class loader monitoring service, and proceeds to step 502 .

Step 502, the class loader monitors the service response, and proceeds to step 503.

Step 503 , judging whether a specific class loader instance is specified in the specified interface call, and if not specified, proceed to step 504 .

Step 504, traverse all saved class loader instances, and go to step 505.

Step 505, judge whether the class loader instance has loaded the class with the given class name, if not loaded the class with the given class name, then return to step 504, if the class with the given class name has been loaded, then go to step 506.

Step 506, constructing a class information value object. The class information includes: external information such as complete class name, physical location of the class file, loaded classloader, and some internal information of the class itself, such as which attributes and methods it has, which class it inherits from, and which interface it implements. The present invention mainly pays attention to the external information of the class, and mainly needs: the complete class name, the physical location of the class file, the complete class name of the classloader that loads this class, and the unique mark of the classloader instance that loads this class in the JVM, and the unique mark is the JVM Automatically assigned, it is a long integer number.

Step 507, return the class information value object.

Referring to FIG. 6 , it shows another flow chart of the present invention for obtaining class loading information when a class with a given class name is loaded, including:

Step 601 , the client/local invokes the Mbean interface of the class loader monitoring service, and proceeds to step 602 .

Step 602 , the class loader monitors the service response, and proceeds to step 603 .

Step 603 , judging whether a specific class loader instance is specified in the specified interface call, and if not specified, proceed to step 604 .

Step 604, traverse all saved class loader instances, and go to step 605.

Step 605 , judging whether the class loader instance has loaded the class with the given class name, if the class with the given class name has not been loaded, then return to step 604 , if the class with the given class name has been loaded, then go to step 606 .

Step 606: Construct a class information value object, the class information value object includes information such as the class loader for loading the class, the physical path of the class file, etc., and add the class information value object into the class information value object set.

Step 607 , judging whether there are class loader instances, if there are class loader instances that have not been traversed, return to step 604 , if all class loader instances have been traversed, proceed to step 608 .

Step 608, return the class information value object set.

Referring to Fig. 7, it shows a kind of flow chart of the method for obtaining the class loading information that the specified class name is loaded in the specified classloader of the present invention, including:

Step 701 , the client/local invokes the Mbean interface of the class loader monitoring service, and proceeds to step 702 .

Step 702, the class loader monitoring service responds to the call, and enters step 703.

Step 703 , judging whether a specific class loader instance is specified in the specified interface call, and if so, proceed to step 704 .

Step 704, judging whether the specified class loader instance has loaded the class with the given class name, if the class with the given class name has not been loaded, return a null value, and if the class with the given class name has been loaded, then enter step 705.

Step 705. Construct a class information value object, which includes information such as the class loader that loads the class, the physical path of the class file, and the like.

Step 706, return the class information value object.

Above, a method for obtaining class loading information in an application server provided by the present invention has been introduced in detail. In this paper, specific examples have been used to illustrate the principle and implementation of the present invention. The descriptions of the above embodiments are only used to help Understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation and scope of application. In summary, the content of this specification is not It should be understood as a limitation of the present invention.

Claims (10)

1. A method for obtaining class loading information in an application server, comprising: Register the listener with the class loader; when the class loader is instantiated, activate said registered listener; the listener accepts a trigger and responds to the trigger; The listener holds a class loader instance reference. 2. The method for obtaining class loading information in an application server according to claim 1, wherein the specific steps of registering a listener include: Implement an Mbean class loader monitoring service that complies with the Java EE specification; Configuring the class loader monitoring service in the startup service list of the application server; Register listeners with the class loader monitoring service. 3. The method for obtaining class loading information in an application server according to claim 1, wherein the specific steps of saving are: The listener saves the class loader instance reference in a data structure in memory. 4. The method for obtaining class loading information in an application server according to claim 1, further comprising: Accept the local/client request, access and output the class loading information corresponding to the class name through the saved class loader according to the requested class name. 5. The method for obtaining class loading information in an application server according to claim 4, wherein the step of outputting class loading information specifically comprises: Call the class loader monitoring service locally; The class loader monitors the service response, accesses and returns the class loading information corresponding to the class name in the saved request through the saved class loader. 6. The method for obtaining class loading information in an application server according to claim 4, wherein said step of outputting class loading information comprises: The client logs in to the application server; Initialize the JMX connector; Obtain the service management component Mbean interface of the specified service name; The information is obtained by calling the interface. 7. The method for obtaining class loading information in an application server according to claim 5 or 6, wherein the specific steps of outputting class loading information include: The client/local invokes the Mbean interface of the service management component of the class loader monitoring service to request the number of class loader instances in the application server; The class loader monitors the service response, returning the number of saved class loader instances. 8. The method for obtaining class loading information in an application server according to claim 5 or 6, wherein the step of outputting the class loading information specifically comprises: a1. The client/local invokes the Mbean interface of the service management component of the class loader monitoring service; a2. The class loader monitors the service response; a3. Determine whether a specific class loader instance is specified in the specified interface call, if not specified, enter step a4; a4. Traverse all saved class loader instances; a5. Determine whether the class loader instance has loaded the class with the given class name, otherwise return to step a4, and if yes, enter step a6; a6. Constructing a class information value object, said class information value object including the class loader for loading the class, and the physical path of the class file; a7. Return the class information value object. 9. The method for obtaining class loading information in an application server according to claim 5 or 6, wherein the step of outputting the class loading information specifically comprises: b1. The client/local invokes the Mbean interface of the service management component of the class loader monitoring service; b2. The class loader monitors the service response; b3. Determine whether a specific class loader instance is specified in the specified interface call, and if not specified, enter step b4; b4. Traverse all saved class loader instances; b5. Determine whether the class loader instance has loaded the class with the given class name, otherwise return to step b4, and if yes, enter step b6; b6, constructing the class information value object, the class information value object including the class loader for loading the class, the physical path of the class file, adding the class information value object into the class information value object collection; b7, judging whether there is a class loader instance, if yes, return to step b4, otherwise enter step b8; b8. Return the class information value object set. 10. The method for obtaining class loading information in an application server according to claim 5 or 6, wherein the step of outputting the class loading information specifically comprises: c1, the client/local calls the service management component Mbean interface of the class loader monitoring service; c2. The class loader monitors the service response; c3. Determine whether a specific class loader instance is specified in the specified interface call, and if so, enter step c4; c4. Determine whether the specified class loader instance has loaded the class with the given class name, otherwise return a null value, and if so, enter step c5; c5. Constructing a class information value object, said class information value object including the class loader for loading the class, and the physical path of the class file; c6. Return the class information value object.

Images