What are the differences between Java request forwarding and request redirection?

Preface

In Java, There are two ways to implement jumps: Request forwarding and request redirection, but the two are completely different, so we will discuss them today. it.

The main differences between request forwarding and request redirection include the following 5 points:

• Different definitions

• Different jump parties

• Different data sharing

• Different final URL address

• Code Implementing different

Next, let’s look at them one by one.

1. Different definitions

Request forwarding (Forward): occurs inside the server program. When the server receives a request from the client, it will first forward the request to target address, and then forward the result returned by the target address to the client. The client has no awareness of all this. This is like Zhang San (client) borrowing money from Li Si (server), and Li Si has no money, so Li Si goes to Wang Wu to borrow money. , and lent the money to Zhang San. During the whole process, Zhang San only borrowed money once, and the rest was done by Li Si. This is the request for forwarding. **Request redirection (Redirect): Request redirection means that after the server receives the client's request, it will return a temporary response header to the client. This temporary response header records that the client needs to send the request again ( Redirect) URL address. After the client receives the address, it will send the request to the new address. This is request redirection. **This is like Zhang San (client) asking Li Si (server) to borrow money. Li Si has no money, so Li Si tells Zhang San, "I have no money, you go to Wang Wu to borrow money." So Zhang San I went to Wang Wu's house again and borrowed money. This was a request for redirection.

2. Different requesting parties

From the above definitions of request forwarding and request redirection, we can see that: Request forwarding is a server-side behavior, and the server replaces the client The client sends a request and returns the result to the client; Request redirection is the behavior of the client , their interaction process, is shown in the following figure:

3. Different data sharing

Request forwarding is implemented on the server side, so during the entire execution process, the client (browser side) only needs to send a request once, so the entire interaction process The same Request request object and a Response response object are used, so the request and returned data are shared during the entire request process; and the request redirection client sends two completely different requests, so in the two requests The data is different.

4. The final URL address is different

Request forwarding is that the server makes the request on its behalf and then returns the result to the client, so the URL address remains unchanged during the entire request process; while the request is repeated Orientation is when the server tells the client, "Go to another place to visit", so the browser will resend the request, so the URL finally displayed by the client is also the final jump address, not the address of the initial request. , so the URL address has changed.

5. Different code implementations

In SpringBoot, the implementation code for request forwarding is as follows:

@RequestMapping("/fw")
public void forward(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    request.getRequestDispatcher("/index.html").forward(request, response);
}

And the implementation of request redirection The code is as follows:

@RequestMapping("/rt")
public void redirect(HttpServletRequest request, HttpServletResponse response) throws IOException {
    response.sendRedirect("/index.html");
}

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