org.apache.catalina.core.DefaultInstanceManager cannot be cast to org.apache.tomcat.InstanceManager

1、控制台报错信息

严重: Servlet.service() for servlet [jsp] in context with path [/Resource] threw exception [java.lang.ClassCastException: org.apache.catalina.core.DefaultInstanceManager cannot be cast to org.apache.tomcat.InstanceManager] with root cause
java.lang.ClassCastException: org.apache.catalina.core.DefaultInstanceManager cannot be cast to org.apache.tomcat.InstanceManager

2、浏览器报错信息

HTTP Status 500 - java.lang.ClassCastException: org.apache.catalina.core.DefaultInstanceManager cannot be cast to org.apache.tomcat.InstanceManager

3、解决方法

原因是 Tomcat 的 catalina.jar 包冲突了。

网上许多人说是修改 tomcat 中 conf 下的 context.xml 配置文件 在 <context></context> 之间加下面的代码 <Loader delegate="true" />

然而我的修改完后还是不行，于是想着要不更换 apache-tomcat 的版本试一试：（结果还是不行）
[Apache Tomcat 各版本下载]

最后把加上去的代码 <Loader delegate="true" /> 给撤回了，修改了 pom.xml 配置得以解决！！

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
  http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  
  <groupId>org.xxx.yyy</groupId>
  <artifactId>XXX</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <finalName>XXX</finalName>
    <pluginManagement>
      <plugins>
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.0.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.7.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.20.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-war-plugin</artifactId>
          <version>3.2.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
        
        <!-- 配置 tomcat7-maven-plugin 插件 -->
        <plugin>
          <groupId>org.apache.tomcat.maven</groupId>
          <artifactId>tomcat7-maven-plugin</artifactId>
          <version>2.2</version>
          <configuration>
            <server>tomcat7</server>
            <username>xxxx</username>
            <password>xxxx</password>
            <uriEncoding>UTF-8</uriEncoding>
            <url>http://localhost:8080/manager/text</url>
          </configuration>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>