Caused by: java.lang.RuntimeException: The Eclipse JDT Core jar is not in the classpath

在操作Drools的测试例子时，Eclipse后台报以下错误：
org.drools.RuntimeDroolsException: Unable to load dialect 'org.drools.rule.builder.dialect.java.JavaDialectConfiguration:java'
 at org.drools.compiler.PackageBuilderConfiguration.addDialect(PackageBuilderConfiguration.java:160)
 at org.drools.compiler.PackageBuilderConfiguration.buildDialectConfigurationMap(PackageBuilderConfiguration.java:146)
 at org.drools.compiler.PackageBuilderConfiguration.init(PackageBuilderConfiguration.java:121)
 at org.drools.compiler.PackageBuilderConfiguration.<init>(PackageBuilderConfiguration.java:98)
 at org.drools.compiler.PackageBuilder.<init>(PackageBuilder.java:124)
 at org.drools.compiler.PackageBuilder.<init>(PackageBuilder.java:86)
 at com.sample.DecisionTableTest.readDecisionTable(DecisionTableTest.java:58)
 at com.sample.DecisionTableTest.main(DecisionTableTest.java:35)
Caused by: java.lang.RuntimeException: The Eclipse JDT Core jar is not in the classpath
 at org.drools.rule.builder.dialect.java.JavaDialectConfiguration.setCompiler(JavaDialectConfiguration.java:91)
 at org.drools.rule.builder.dialect.java.JavaDialectConfiguration.init(JavaDialectConfiguration.java:52)
 at org.drools.compiler.PackageBuilderConfiguration.addDialect(PackageBuilderConfiguration.java:156)
 ... 7 more

主要是缺少一个jar包：org.eclipse.jdt.core_3.3.1.v_780_R33x.jar而引起的。