“No primary or single unique constructor found for interface javax.servlet.http.HttpSession”Bug修复

Bug复现

今天在写SpringBoot应用时，写一个后端生成图形验证码的业务时，需要用到session保存后端生成的图形验证码的Base64编码，然后前端通过session来显示图形验证码。

代码里用到了servlet里的HttpSession类，于是idea自动导入了javax.servlet包里的HttpSession。

业务代码如下：

package cn.edu.wit.controller;

import cn.edu.wit.entity.Result;
import com.google.code.kaptcha.impl.DefaultKaptcha;
import com.google.code.kaptcha.util.Config;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
// 注意这里导入的是javax.servlet包
import javax.servlet.http.HttpSession;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.util.Base64;
import javax.imageio.ImageIO;

@Slf4j
@RestController
public class CaptchaController {
    private DefaultKaptcha captchaProducer;

    public CaptchaController() {
        // 配置Kaptcha
        captchaProducer = new DefaultKaptcha();
        captchaProducer.setConfig(new Config(new java.util.Properties()));
    }

    @GetMapping("/captcha")
    public Result getCaptcha(HttpSession session) throws Exception {
        // 生成验证码文本
        String captchaText = captchaProducer.createText();
        log.info("验证码: " + captchaText);
        // 将验证码文本存储在Session中
        session.setAttribute("captcha", captchaText);

        // 生成验证码图片
        BufferedImage image = captchaProducer.createImage(captchaText);
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        ImageIO.write(image, "jpg", outputStream);
        // 转换为Base64
        String base64Image = Base64.getEncoder().encodeToString(outputStream.toByteArray());

        // 返回给前端Base64编码的图形验证码
        return Result.success("data:image/jpeg;base64," + base64Image);
    }
}

Postman 测试如下：

GET http://localhost:8080/captcha

启动SpringBoot应用后，测试Postman接口，idea控制台报错：

java.lang.IllegalStateException: No primary or single unique constructor found for interface javax.servlet.http.HttpSession
	at org.springframework.beans.BeanUtils.getResolvableConstructor(BeanUtils.java:267)
	at org.springframework.validation.DataBinder.createObject(DataBinder.java:924)
	at org.springframework.validation.DataBinder.construct(DataBinder.java:903)
	at org.springframework.web.bind.ServletRequestDataBinder.construct(ServletRequestDataBinder.java:116)
	at org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor.constructAttribute(ServletModelAttributeMethodProcessor.java:156)
	at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.resolveArgument(ModelAttributeMethodProcessor.java:148)
	at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:122)
	at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:225)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:178)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:118)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:917)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:829)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1089)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:903)
	at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:564)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885)
	at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:205)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:482)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:340)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:391)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:896)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1744)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.base/java.lang.Thread.run(Thread.java:842)

Bug原因

从stackoverflow社区找到了错误原因和解决方案

错误原因原文如下：

Spring Boot 3 (and Spring Framework 6) require a baseline of Jakarte EE 10. You cannot use it with Java EE or Jakarte EE versions below that.

You have to remove the explicit dependency on jakarta.servlet-api from your pom.xml. Java Servlet 4 is below the baseline and in particular still uses the package names starting with javax.servlet.

中文机翻：

Spring Boot 3（和 Spring Framework 6）需要 Jakarte EE 10 的基线。您不能将其与 Java EE 或低于该版本的 Jakarte EE 版本一起使用。

您必须jakarta.servlet-api从您的pom.xml. Java Servlet 4 低于基线，特别是仍然使用以javax.servlet.

也就是说：SpringBoot3已经不支持javax.servlet包里的HttpSession了，如果需要使用该类的话，需要导入jakarta.servlet包里的HttpSession。

Bug修复

原作者给出的解决方案如下：

If you remove the explicit dependency, Spring will pull in transitively the correct one. You then need to replace all imports starting with javax.servlet with javax replaced by jakarta, e.g.

import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServletResponse;

 bug修复方法很简单，就是将所有的javax.servlet包替换成jakarta.servlet包。

例如我的代码里就应该这样修改：

// import javax.servlet.http.HttpSession;
// 将javax替换成jakarta
import jakarta.servlet.http.HttpSession;

修改后，重新运行SpringBoot应用即可正常生成图形验证码，并保存到session里返回给前端。

参考资料

Fix “No primary or single unique constructor found for interface javax.servlet.http.HttpServletResponse” in Spring Boot application