我尝试从 XML 配置创建求解器。但是整个过程会返回一条毫无意义的神秘错误消息。
我该如何解决?我怎样才能理解这一点来实际解决类似的问题?
jesvin@Jesvin-Technovia:~/dev/drools/sudoku$ java App
Exception in thread "main" java.lang.NullPointerException
at org.drools.planner.core.domain.solution.SolutionDescriptor.processPropertyAnnotations(SolutionDescriptor.java:69)
at org.drools.planner.core.domain.solution.SolutionDescriptor.<init>(SolutionDescriptor.java:61)
at org.drools.planner.config.solver.SolverConfig.buildSolutionDescriptor(SolverConfig.java:197)
at org.drools.planner.config.solver.SolverConfig.buildSolver(SolverConfig.java:167)
at org.drools.planner.config.XmlSolverConfigurer.buildSolver(XmlSolverConfigurer.java:103)
at App.createSolver(App.java:62)
at App.main(App.java:40)
抛出它的函数在此处列出。当然是行return configurer.buildSolver();
。
private static Solver createSolver(){
XmlSolverConfigurer configurer = new XmlSolverConfigurer();
File file = new File("solver.xml");
FileInputStream fin = null;
try{
fin = new FileInputStream(file);
}
catch(IOException e){
System.out.println("Unable to read drl");
}
configurer.configure(fin);
//configurer.configure("/home/jesvin/dev/drools/sudoku/solver.xml");
return configurer.buildSolver();
}
XML 的内容:
<?xml version="1.0" encoding="UTF-8"?>
<solver>
<environmentMode>DEBUG</environmentMode>
<solutionClass>domain.Sudoku</solutionClass>
<planningEntityClass>domain.Digit</planningEntityClass>
<scoreDrl>score.drl</scoreDrl>
<scoreDefinition>
<scoreDefinitionType>SIMPLE</scoreDefinitionType>
</scoreDefinition>
<termination>
<scoreAttained>0</scoreAttained>
</termination>
<!--
<constructionHeuristic>
<constructionHeuristicType>FIRST_FIT_DECREASING</constructionHeuristicType>
<constructionHeuristicPickEarlyType>FIRST_LAST_STEP_SCORE_EQUAL_OR_IMPROVING</constructionHeuristicPickEarlyType>
</constructionHeuristic> -->
<constructionHeuristic>
<constructionHeuristicType>FIRST_FIT</constructionHeuristicType>
<moveFactoryClass>solution.RowChangeMoveFactory</moveFactoryClass>
</selector>
<acceptor>
<completeSolutionTabuSize>1000</completeSolutionTabuSize>
</acceptor>
<forager>
<!-- Real world problems require to use of <minimalAcceptedSelection> -->
</forager>
</localSearch>
</solver>