In -depth interpretation of the technical principles of the Jakarta Interceptors framework in the Java library
In -depth interpretation of the technical principles of the Jakarta Interceptors framework in the Java library
introduction:
In the development of Java, the interceptor is a very important technology that can help us achieve a series of cross -sectional attention points such as separation of attention point separation, log records, transaction management, and security verification.Jakarta Interceptors (formerly known as CDI Interceptors) is a standard interceptor framework under the Jakarta EE specification.This article will interpret the technical principles of the Jakarta Interceptors framework in detail to help readers better understand and apply interceptor technology.
1. Overview of Jakarta Internet
Jakarta Interceptors is a lightweight interceptor framework introduced in the Jakarta EE 8 specification. It allows developers to declare and apply interceptors by annotating and applying to intercept and enhance the application behavior.
The interceptor has the same life cycle as the intercepted class or method.During the method calling process, the interceptor can insert specific operations, such as pre -processing, rear processing, surrounding treatment, etc. to achieve the processing of cross -section attention.
Second, the application scenario of Jakarta Internet
1. Logging: The parameters and return values of the interceptor capture method can be recorded, and related log information can be recorded in order to check and analyze the problems.
2. Affairs management: The interceptor can be turned on and submitted to the transaction through the method to ensure the consistency of the data.
3. Security verification: You can use the interceptor to verify the permissions before the method executes to ensure that only users with sufficient permissions can perform the corresponding operation.
Third, the principle of implementation of Jakarta Internet
1. Note declaration:
In the Java code, a interceptor can be declared by using annotations provided by Jakarta Interceptors.Commonly used declarations include:
-@Interceptor: It is used to identify a class as an interceptor.
-@Aroundinvoke: It is used to identify a method as an interception method. The interceptor will execute this method before and after the target method executes.
-@Interceptors: Used to apply one or more interceptors to class or methods.
2. Create the interception chain:
When the application starts, the Jakarta Interceptors scan and analyze all interceptor annotations, and create a blocking chain according to the sequential order of the interceptor.Each interceptor in the interception chain is called at different stages of the method execution, including before the method starts, after the method is ended, and the method execution is abnormal.
3. Calling the interceptor:
When an interception method is called, the interceptor in the interceptor chain will be executed in order in the order of the statement.At each interception point, the interceptor can select the execution of the suspension method, the input parameters of the modification method, the return value of the modification method, or throw an exception.
Fourth, Jakarta Interceptors code example
The following is a simple example of using Jakarta Interceptors:
@Interceptor
public class LogInterceptor {
@AroundInvoke
public Object logMethod(InvocationContext context) throws Exception {
System.out.println("Enter method: " + context.getMethod().getName());
try {
return context.proceed();
} finally {
System.out.println("Exit method: " + context.getMethod().getName());
}
}
}
@Path("/example")
public class ExampleResource {
@Inject
private ExampleService exampleService;
@GET
@LogInterceptor
public String getExample() {
return exampleService.getExampleData();
}
}
public class ExampleService {
public String getExampleData() {
return "This is example data.";
}
}
In the above code, we define an interceptor called Loginterceptor, which is identified by using @Interceptor annotation.In Loginterceptor, we use the @AaroundinVoke annotation to declare a blocking method LogmetHod, which will be called before and after being executed by the interception method.
In the ExamPleresource class, we apply LogInterceptor to the Getexample method by using @loginterceptor annotation.In this way, every time the Getexample method is called, the logMethod method of Loginterceptor is called.
Summarize:
Through in -depth interpretation of the Jakarta Interceptors framework, we understand its technical principles and how to use it.By flexibly applying the interceptor, we can realize a series of functions such as focus separation, log records, transaction management, and security verification to improve the elasticity and maintenance of the application.
