我正在通过https://docs.jboss.org/jbpm/release/7.1.0.Final/jbpm-docs/html_single/#_jbpminstaller的jbpm官方文档创建一个示例Jbpm项目 而ant start.demo成功了，当我继续从Eclipse创建新的jBPM项目时，我得到以下错误 -
Errors occurred during the build.
Errors running builder 'Drools Builder' on project 'Demo'.
Could not initialize class org.kie.api.KieServices$Factory
请建议。