添加tomcat-embed-jasper后JSP白标404且项目报错、找不到主类求助

Hey there! I’ve dealt with these exact headaches when setting up JSP in Spring Boot, so let’s walk through the fixes step by step:

1. Fix Your Tomcat Embed Jasper Dependency #

Spring Boot has specific requirements for JSP support. Your current dependency is missing key pieces, and the scope might be off. Update your pom.xml dependencies like this:

<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-jasper</artifactId>
    <!-- Use 'compile' for embedded Tomcat; switch to 'provided' if deploying as a WAR to external Tomcat -->
    <scope>compile</scope>
</dependency>
<!-- Add JSTL (required for JSP tag libraries) -->
<!-- For Spring Boot 2.x -->
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>jstl</artifactId>
</dependency>
<!-- For Spring Boot 3.x, replace the above with Jakarta EE versions -->
<!--
<dependency>
    <groupId>jakarta.servlet.jsp.jstl</groupId>
    <artifactId>jakarta.servlet.jsp.jstl-api</artifactId>
</dependency>
<dependency>
    <groupId>org.glassfish.web</groupId>
    <artifactId>jakarta.servlet.jsp.jstl</artifactId>
</dependency>
-->

2. Double-Check Your Project Structure #

Spring Boot is picky about where JSP files live. Your application.properties points to /WEB-INF/views/, so your project must follow this structure exactly:

src
├── main
│   ├── java
│   │   └── your/package/with/MainApplication.java (the one with @SpringBootApplication)
│   ├── resources
│   │   └── application.properties
│   └── webapp
│       └── WEB-INF
│           └── views
│               └── your-page.jsp
└── pom.xml

• If you don’t have a webapp folder, create it under src/main.
• In IDEA, right-click the webapp folder and select Mark Directory as > Web Resource Directory so the IDE recognizes it correctly.

3. Fix the "Could Not Find or Load Main Class" Error #

This almost always ties to Maven configuration or project structure:

• First, confirm your main class (with @SpringBootApplication) is in src/main/java and not in an excluded subfolder.
• Make sure your pom.xml has the correct Spring Boot Maven plugin configuration. If your main class isn’t in the root package, explicitly set it:

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <configuration>
                <mainClass>your.package.path.MainApplication</mainClass>
            </configuration>
        </plugin>
    </plugins>
</build>

• Also, note that Spring Boot’s JAR format has limitations with JSP—consider switching to WAR packaging by adding <packaging>war</packaging> to your pom.xml if you run into persistent issues.

4. Refresh Dependencies and Clear Caches #

That red project marker often means Maven dependencies are out of sync:

• Run mvn clean install in your terminal to rebuild dependencies and the project.
• In your IDE, clear cached data:
  • IDEA: Go to File > Invalidate Caches... > Invalidate and Restart
  • Eclipse: Go to Project > Clean... and select your project

5. Verify Your application.properties #

Your config looks right, but double-check for typos or extra spaces. If you’re on Spring Boot 2.6+, you might also want to add:

spring.mvc.view.allow-request-override=true

This isn’t always necessary, but it can fix edge-case JSP rendering issues.

Give these steps a try—they should resolve all your issues!

内容的提问来源于stack exchange，提问作者Gana