dubbo2.5.3升级到dobbo2.8.4(dubbox) jar

需要注意的地方：

1、pom文件中 dubbo的版本由2.5.3变为2.8.4，maven依赖如下：

    <dependency>

        <groupId>com.alibaba</groupId>

        <artifactId>dubbo</artifactId>

        <version>2.8.4</version>

        <exclusions> ---去除掉dubbo自带依赖的spring2.5.X，升级为3.x

            <exclusion>

                <artifactId>spring</artifactId>

                <groupId>org.springframework</groupId>

            </exclusion>

        </exclusions>

    </dependency>

2、添加javassist的jar包maven依赖如下：

    <dependency>

            <groupId>javassist</groupId>

            <artifactId>javassist</artifactId>

            <version>3.12.1.GA</version>

    </dependency>

3、添加netty的jar包maven依赖如下：

    <dependency>

            <groupId>io.netty</groupId>

            <artifactId>netty</artifactId>

            <version>3.7.0.Final</version>

    </dependency>