SpringBoot使用devtools导致的类型转换异常

问题：

最近在使用新框架SpringBoot + shiro + spring-data-jpa时，为了体验下spring自带的热部署工具的便捷，于是引入了

<dependency>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-devtools</artifactId>

<!-- optional=true,依赖不会传递，该项目依赖devtools；之后依赖myboot项目的项目如果想要使用devtools，需要重新引入 -->

<optional>true</optional>

</dependency>

在起初并没遇到什么问题，当使用shiro的session管理，而且用的sessionDao是redis实现的，然后再使用Session存取属性时，发现存进去的属性，再取出来后，就会出现类型转换异常ClassCastException

分析：

然后自己写了一大推单元测试模拟就是没问题，后来突然意识到会不会是因为ClassLoader不同导致的类型转换异常呢，然后注意了下项目启动时加载项目中的类使用的加载器都是

org.springframework.boot.devtools.restart.classloader.RestartClassLoader

而从shiro session 取出来的对象（从redis中取出经过反序列化）的类加载器都是

sun.misc.Launcher.AppClassLoader

很明显会导致类型转换异常，原来Spring的dev-tools为了实现重新装载class自己实现了一个类加载器，来加载项目中会改变的类，方便重启时将新改动的内容更新进来，其实其中官方文档中是有做说明的：

By default, any open project in your IDE will be loaded using the
“restart” classloader, and any regular .jar file will be loaded using
the “base” classloader. If you work on a multi-module project, and not
each module is imported into your IDE, you may need to customize
things. To do this you can create a
META-INF/spring-devtools.properties file.
The spring-devtools.properties file can contain restart.exclude. and
restart.include. prefixed properties. The include elements are items
that should be pulled up into the “restart” classloader, and the
exclude elements are items that should be pushed down into the “base”
classloader. The value of the property is a regex pattern that will be
applied to the classpath.

解决：

方案一、解决方案就是在resources目录下面创建META_INF文件夹，然后创建spring-devtools.properties文件，文件加上类似下面的配置：

restart.exclude.companycommonlibs=/mycorp-common-[\w-]+.jar

restart.include.projectcommon=/mycorp-myproj-[\w-]+.jar

All property keys must be unique. As long as a property starts with
restart.include. or restart.exclude. it will be considered. All
META-INF/spring-devtools.properties from the classpath will be loaded.
You can package files inside your project, or in the libraries that
the project consumes.

方案二、不使用spring-boot-devtools