Java project debugging practice: How to efficiently debug GET requests in Spring Boot projects and solve case inconsistencies through equalsIgnoreCase()

write at the front

Recently, I encountered a problem while running a java project.

Under the remote guidance of @tanyue , during the step-by-step debugging process, it was found that the case was inconsistent, which led to the judgment that the fields were not the same.

Finally, after replacing equals() with equalsIgnoreCase(), the problem was successfully solved!

equals() will judge the case difference, but equalsIgnoreCase() will not judge the case.

I haven’t touched Java for a long time. I learned something new about debugging while watching, so I’ll record it here.

The whole process

During the development of a recent Java project, I encountered a puzzling problem. The project works fine for the most part, but in some specific cases it doesn't work as expected. At first, I thought it was a logical error or some hidden bug, but after carefully reviewing the code, no obvious errors were found.

Mr. Dan Da helped with remote guidance. Thank you again for his time and energy. During this period, because I have dual screens, some operations are a bit complicated and strangehh.

In order to locate the problem, we started a detailed debugging process. By printing logs and tracing step by step, I found that the problem was with the case of the string. In Java, the default string comparison is case-sensitive. This means that even if two strings have the same literal value but inconsistent case, equals()they will be considered unequal when compared using the method.

The problem is: when two seemingly identical strings are compared, the result is not "equal" as expected.
In this project, there was a case inconsistency because some fields were entered by the user and others were generated by the system. This is why in some cases, even if the fields appear to be the same, the program determines that they are not equal.

The final solution was quite simple, yet very effective. equals()Replace all method calls involving strings with equalsIgnoreCase(). This method solved my problem by ignoring case differences when comparing strings. For example, "example".equalsIgnoreCase("Example")will return true, while using equals()will return false.

This experience taught me to be extra careful when dealing with string comparisons, especially in scenarios involving user input and system-generated data. I also realize that sometimes the solution to a problem can be surprisingly simple, and the key is patience and careful debugging.

Java equalsIgnoreCase() method

Reference : https://www.runoob.com/java/java-string-equalsignorecase.html

Java String class : equalsIgnoreCase() method is used to compare a string with the specified object, regardless of case.

grammar :

public boolean equalsIgnoreCase(String anotherString)

Parameters : anObject – the object to compare the string to.

Return value : true if the given object is equal to the string, false otherwise.

Example : equals() will determine the case difference, but equalsIgnoreCase() will not determine the case difference:

public class Test {
    
    
    public static void main(String args[]) {
    
    
        String Str1 = new String("runoob");
        String Str2 = Str1;
        String Str3 = new String("runoob");
        String Str4 = new String("RUNOOB");
        boolean retVal;

        retVal = Str1.equals( Str2 );
        System.out.println("返回值 = " + retVal );

        retVal = Str3.equals( Str4);
        System.out.println("返回值 = " + retVal );

        retVal = Str1.equalsIgnoreCase( Str4 );
        System.out.println("返回值 = " + retVal );
    }
}

The execution result of the above program is:

返回值 = true
返回值 = false
返回值 = true

How to debug SpringBoot project in idea

Debugging in a Spring Boot project, especially for network requests such as HTTP GET requests, can be done in the IDE by following the steps below. Here are the steps:

In IntelliJ IDEA, you can directly invoke a GET request in a Spring Boot project without using external tools such as Postman or a browser. IntelliJ IDEA provides a built-in HTTP client functionality that allows sending HTTP requests and viewing responses directly from the IDE.

Using the built-in HTTP client in IntelliJ IDEA

1. Create HTTP request file:

   • In the project, right-click the source code directory or any directory.
   • Select New-> HTTP Request.
   • This will create a new .httpfile.

2. Write HTTP request: (You can also click to automatically generate)

   • In .httpthe file, write a GET request. For example:

     GET http://localhost:8080/your-endpoint
     

   • Ensure that the URL and port number are consistent with the Spring Boot application configuration and replaced your-endpointwith the actual endpoint path.

3. send request:

   • In .httpthe file, click the green play button next to the request line to send the request.
   • You can also use shortcut keys (usually Ctrl + Enter).

4. View the response:

   • After sending the request, the IDE displays a new window or area where the HTTP response can be seen.
   • The response includes status code, header information and response body.

Set breakpoints and debug

If you want to debug while handling this GET request:

1. Set breakpoint:

   • Find the part of the code you want to debug, such as the method that handles GET requests in a Controller.
   • Set a breakpoint next to the line of code where you want the program to pause execution. Just click on the empty space next to the line number and you'll see a red dot indicating that the breakpoint has been set.

2. Start the app in debug mode:

   • Next to the project's startup class (usually @SpringBootApplicationthe class annotated), click the debug button (an icon similar to a bug) or use the shortcut key (usually Shift+F9) to start debugging mode.

3. Send a GET request:

   • Use a browser, Postman, or any HTTP client to make a GET request to the Spring Boot application, making sure to use the correct URL and port number.
   • In IntelliJ IDEA, you can directly invoke a GET request in a Spring Boot project without using external tools such as Postman or a browser. IntelliJ IDEA provides a built-in HTTP client functionality that allows sending HTTP requests and viewing responses directly from the IDE.

4. Debugging and inspection :

   • When a request reaches a breakpoint, the application pauses at that point.
   • At this time, you can check and modify variable values ​​and observe the application status.
   • Step through code using functions such as Step Over (F8) and Step Into (F7).

5. View request details :

   • At the breakpoint, you can view the detailed information of the HTTP request, such as request parameters, request headers, etc.

6. Adjust response and continue execution :

   • If necessary, you can modify variable values ​​or adjust the response in the debugger.
   • Continue program execution until a response is returned.

7. Logs and output :

   • View the IDE's console output for log and program output information.

8. Conditional breakpoint :

   • If you want to pause execution only when a specific condition is met, you can set a conditional breakpoint.

9. End the debugging session :

   • After debugging is complete, click the "Stop" button to end the debugging session.

10. Use log printing :

    • If you do not want to interrupt the execution flow, you can add log printing statements to the code to track the execution of the program.

Note that when debugging network requests, ensure that the network environment is configured correctly, especially proxy settings, port configuration, etc., to ensure that the request can reach your Spring Boot application. Through such a debugging process, you can understand and process GET requests in Spring Boot applications in detail.

Using this approach, it is easy to have complete control over the sending and receiving of HTTP requests from within the IDE, while enabling efficient debugging. This is very convenient for quickly testing and debugging REST APIs in Spring Boot applications.

Supplement: How to debug java projects in idea

Debugging Java projects in IntelliJ IDEA is a powerful and essential feature, especially crucial for identifying and solving complex problems. Here are the steps on how to debug a Java project in IntelliJ IDEA:

1. Set breakpoint :

   • Open the Java project and find the part you want to debug.
   • Click next to the line number or use the shortcut key (on Windows/Linux Ctrl+F8, on Mac Cmd+F8) to set a breakpoint at the line of code where you want the program to pause.

2. Start a debugging session :

   • You can start a debugging session by clicking the "bug" icon (debug icon) on the IDE interface, or using the shortcut key ( Shift+F9).
   • Make sure the project has been compiled and run with the correct configuration.

3. View variables and expressions :

   • When program execution reaches a breakpoint, it will pause. At this point, the value of the variable can be viewed and evaluated.
   • Use the Variables window to view variables in the current scope.
   • Specific expressions can be evaluated using the expression evaluation function.

4. Step through the code :

   • Use "Step Over" (F8) to execute the current line of code and move to the next line.
   • Use "Step Into" (F7) to enter a method if there is a method call.
   • Use "Step Out" (Shift+F8) to exit the current method and return to the place where it was called.

5. View logs and output :

   • View the Console window for program output and log information.

6. Modify variable value :

   • During debugging, the values ​​of variables can be modified dynamically to test different situations.

7. Conditional breakpoint :

   • If you only want to pause execution when a specific condition is met, you can set a conditional breakpoint. Right click on the breakpoint and add condition.

8. Watch expression :

   • In the Watches window, you can add specific expressions or variables that need to be monitored.

9. End the debugging session :

   • Once you are done debugging, you can click the "Stop" button (red square icon) to terminate the debugging session.

10. Use log breakpoints :

    • Log breakpoints allow specific information to be printed out without pausing the program, which is useful for debugging without interrupting the flow of the application.