An in-depth exploration of the chain of responsibility pattern in Java design patterns

The Chain of Responsibility pattern is a design pattern that allows you to pass requests to a set of objects in order until the request is processed or all objects have tried to process it. It contains the following components: Handler, abstract Handler and Client. Advantages include: loose coupling, scalability, and reusability. Filter chains are a common practical example.

In-depth exploration of the chain of responsibility pattern of Java design patterns

Introduction

The Chain of Responsibility pattern is a design pattern that allows you to create a set of objects that handle requests in sequence. When an object cannot handle a request, it passes the request to the next object in the chain.

Structure

The chain of responsibility pattern contains the following components:

• ##Handler: An object that handles requests.
• Abstract Handler: Define the interface of Handler.
• Client: The object that initiates the request.

Working Principle

Customer to the first processor in the chain Send a request.
1. The processor decides whether to process the request. If so, process the request and return the result. If not, it passes the request to the next processor in the chain.
2. This process repeats until one processor handles the request or all processors in the chain have attempted to handle the request.

Advantages

• Loose coupling: Processor Independent of each other, easy to add or remove processors.
• Scalability: Additional processing steps can be easily added as needed.
• Reusability: Processors can be reused to handle different types of requests.

Practical case

Filter chain

public class FilterChain {

    private List<Filter> filters;

    public FilterChain(List<Filter> filters) {
        this.filters = filters;
    }

    public void doFilter(Request request, Response response) {
        for (Filter filter : filters) {
            filter.doFilter(request, response);
        }
    }
}

public interface Filter {
    
    void doFilter(Request request, Response response);
}

public class AuthenticationFilter implements Filter {

    @Override
    public void doFilter(Request request, Response response) {
        // 验证请求
    }
}

public class AuthorizationFilter implements Filter {

    @Override
    public void doFilter(Request request, Response response) {
        // 授权请求
    }
}

public class LoggingFilter implements Filter {

    @Override
    public void doFilter(Request request, Response response) {
        // 记录请求和响应
    }
}

public class Main {

    public static void main(String[] args) {
        FilterChain filterChain = new FilterChain(
            List.of(new AuthenticationFilter(),
                new AuthorizationFilter(),
                new LoggingFilter())
        );

        filterChain.doFilter(request, response);
    }
}

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