ClassCastException in between equal classes Wildfl

问题:

I am Creating a RESTful application and I am having trouble making a conversion for a new connection. My application server is Wildfly 10.0.

DataSource and Driver in standalone-full.xml:

<datasource jndi-name="java:jboss/datasources/PostgreDS" pool-name="PostgreDS" enabled="true" use-java-context="true">
    <connection-url>jdbc:postgresql://192.168.0.112:5432/bdns</connection-url>
    <driver>postgresql</driver>
    <transaction-isolation>TRANSACTION_READ_COMMITTED</transaction-isolation>
    <pool>
        <min-pool-size>10</min-pool-size>
        <max-pool-size>40</max-pool-size>
        <prefill>true</prefill>
    </pool>
    <security>
        <user-name>sa</user-name>
        <password>000000</password>
    </security>
    <statement>
        <prepared-statement-cache-size>32</prepared-statement-cache-size>
        <share-prepared-statements>true</share-prepared-statements>
    </statement>
</datasource>
<drivers>
    <driver name="postgresql" module="org.postgresql">
        <xa-datasource-class>org.postgresql.xa.PGXADataSource</xa-datasource-class>
    </driver>
</drivers>

Java code ConnectionMng.java:

package dao;

import java.sql.Connection;
import java.sql.SQLException;

import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;

import org.jboss.jca.adapters.jdbc.jdk7.WrappedConnectionJDK7;
import org.postgresql.jdbc.PgConnection;

public class ConnectionMng {
    private DataSource ds;

    private ConnectionMng() throws NamingException {
        this.ds = (DataSource)new InitialContext().lookup("java:jboss/datasources/PostgreDS");
    }

    public PgConnection getPgConnection() throws SQLException {
        WrappedConnectionJDK7 wrappedConn = (WrappedConnectionJDK7)ds.getConnection();
        Connection underlyingConn = wrappedConn.getUnderlyingConnection(); 
        return (PgConnection)underlyingConn;
    }
}

Exception occurred:

ClassCastException: org.jboss.jca.adapters.jdbc.jdk7.WrappedConnectionJDK7 cannot be cast to org.jboss.jca.adapters.jdbc.jdk7.WrappedConnectionJDK7

pom.xml:

<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>Core</groupId>
<artifactId>Core</artifactId>
<version>1.0.0-SNAPSHOT</version>
<packaging>war</packaging>
<name>Core</name>
<description>Core</description>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <java.version>1.8</java.version>
    <javac.target>1.8</javac.target>
    <postgresql.enforce.jdk.version>[1.7,1.8)</postgresql.enforce.jdk.version>
</properties>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.3.3.RELEASE</version>
</parent>

<dependencies>
    <dependency>
        <groupId>org.wildfly</groupId>
        <artifactId>wildfly-connector</artifactId>
        <version>10.0.0.Final</version>
    </dependency>
    <dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
    </dependency>
    <dependency>
        <groupId>javax</groupId>
        <artifactId>javaee-api</artifactId>
        <version>7.0</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>servlet-api</artifactId>
        <version>2.5</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-tomcat</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-dbcp2</artifactId>
    </dependency>
    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-mapper-asl</artifactId>
        <version>1.9.13</version>
    </dependency>
    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi-ooxml</artifactId>
        <version>3.12</version>
    </dependency>
    <dependency>
        <groupId>commons-fileupload</groupId>
        <artifactId>commons-fileupload</artifactId>
        <version>1.3.1</version>
    </dependency>
    <dependency>
        <groupId>com.thoughtworks.xstream</groupId>
        <artifactId>xstream</artifactId>
        <version>1.4.8</version>
    </dependency>
    <dependency>
        <groupId>com.github.junrar</groupId>
        <artifactId>junrar</artifactId>
        <version>0.7</version>
    </dependency>
    <dependency>
        <groupId>org.zeroturnaround</groupId>
        <artifactId>zt-zip</artifactId>
        <version>1.9</version>
        <type>jar</type>
        <exclusions>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-log4j12</artifactId>
            </exclusion>
            <exclusion>
                <groupId>log4j</groupId>
                <artifactId>log4j</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
</dependencies>

<build>
    <sourceDirectory>src</sourceDirectory>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
        <plugin>
            <artifactId>maven-war-plugin</artifactId>
            <configuration>
                <warSourceDirectory>WebContent</warSourceDirectory>
                <failOnMissingWebXml>false</failOnMissingWebXml>
            </configuration>
        </plugin>
    </plugins>
</build>

回答1:

The answer from aribeiro is the right answer: A jar, packaged by the build-tool(Maven) is in the lib-directory of the war and conflicts with the wildfly-Classloader.

Additional,here is a generic solution for the following issue:

• you've got a JBoss 7 AS or a Wildfly AS
• You work with Eclipse JBoss Tools
• you deploy an EAR or a WAR, lib-Folder is packed by build-tool like Maven
• there occurs an error like this: examplepackage.ExcampleClass cannot be cast to examplepackage.ExcampleClass

Mostly it happens, when you leave the Java EE-Spec and use JBoss/Wildfly-specific modules, ironjacamar, jsf-impl and so on. Maven puts the required jars in the lib-directory. But the Jars are already in the module-directory of the AS. According to my experience, the ClassCastException occurs for this reason.

You must then remove the jar from the lib-directory, in maven by declaring the dependency as provided.

Tell the JBoss/Wildfly-Classloader, where to find the class. This can be done by:

• Either add a dependency to the MANIFEST.MF of the project. Eclipse-JBoss-Tools loads the class from the Server-Enviroment, so you can remove the dependency from the pom. In your case:

  Dependencies: org.jboss.ironjacamar.jdbcadapters
  

• Or you use the jboss-deployment-structure.xml, then you can load the class with Maven, but declare it as provided

  <dependencies>
      <module name="org.jboss.ironjacamar.jdbcadapters" />
  </dependencies>
  

See also https://docs.jboss.org/author/display/WFLY8/Class+Loading+in+WildFly

回答2:

Clearly, as already stated, you're having a classloader issue due to a dependency clash.

To solve it, you should mark your wildfly-connector dependency as provided.

<dependency>
    <groupId>org.wildfly</groupId>
    <artifactId>wildfly-connector</artifactId>
    <version>10.0.0.Final</version>
    <scope>provided</scope>
</dependency>

WildFly already contains the JAR. If you go to the following folder you can find it:

<wildfly-10.0.0.Final-dir>\modules\system\layers\base\org\jboss\as\connector\main

There's no need for you to pack it with your application.

Nevertheless, as stated on WildFly 10's Implicit module dependencies for deployments, one needs to trigger the JCA sub-system explicitly. For that, one can make use of jboss-deployment-structure.xml with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<jboss-deployment-structure>
    <deployment>
        <dependencies>
            <module name="org.jboss.ironjacamar.jdbcadapters" slot="main"/>            
        </dependencies>
    </deployment>
</jboss-deployment-structure>

Then, add your jboss-deployment-structure.xml to the WEB-INF folder of your WAR.