Mvel迭代一个列表
我有这个类层次结构
StudentClass .java
public class StudentClass { private List studentList; public List getStudentList() { return studentList; } public void setStudentList(List studentList) { this.studentList = studentList; } } Student.java
public class Student { private Child child; private int studAge; public Student(Child child, int studAge) { this.child = child; this.studAge = studAge; } public Child getChild() { return child; } public void setChild(Child child) { this.child = child; } public int getStudAge() { return studAge; } public void setStudAge(int studAge) { this.studAge = studAge; } }
Child.java
public class Child { private String name; private int age; public Child(String name, int age) { this.name = name; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }
主要课程
通过一些逻辑，我构建了这个表达式，通过MVEL执行。 当child2为null时 ，这段代码工作正常，但当child2为null时 ， 它会给出以下错误 。 这是一个有效的场景，它只是我的应用程序中的实体的副本。 在Parent中，Child可能会为null。
仅当对象在索引0处为空时才会出现问题，其余所有索引都可以正常工作，即使索引1为空，索引0如果条件失败，则它将在索引2处执行
public class MvelTest { public static void main(String args[]) throws Exception { String s = "if(contextObjectStudentClass.?studentList != null ){ foreach ( loopVariable0 : contextObjectStudentClass.?studentList){if ( loopVariable0.?child.?age==21 ){return loopVariable0.?child.?name ;}}}return null ;"; Child child2 = new Child("ankur", 23); Child child1 = null; Child child3 = new Child("ankurs", 21); Student s1 = new Student(child1, 21); Student s2 = new Student(child2, 23); Student s3 = new Student(child3, 27); List studentList = new ArrayList(); studentList.add(s1); studentList.add(s2); studentList.add(s3); StudentClass class1 = new StudentClass(); class1.setStudentList(studentList); Map map = new HashMap(); map.put("contextObjectStudentClass", class1); System.out.println(MVEL.eval(s, map)); } }
例外
Exception in thread "main" java.lang.RuntimeException: cannot invoke getter: getChild (see trace) at org.mvel2.optimizers.impl.refl.nodes.GetterAccessor.getValue(GetterAccessor.java:70) at org.mvel2.optimizers.impl.refl.nodes.VariableAccessor.getValue(VariableAccessor.java:37) at org.mvel2.optimizers.dynamic.DynamicGetAccessor.getValue(DynamicGetAccessor.java:73) at org.mvel2.ast.ASTNode.getReducedValueAccelerated(ASTNode.java:108) at org.mvel2.ast.BinaryOperation.getReducedValueAccelerated(BinaryOperation.java:114) at org.mvel2.compiler.ExecutableAccessor.getValue(ExecutableAccessor.java:38) at org.mvel2.ast.IfNode.getReducedValueAccelerated(IfNode.java:73) at org.mvel2.compiler.ExecutableAccessor.getValue(ExecutableAccessor.java:38) at org.mvel2.ast.ForEachNode.getReducedValue(ForEachNode.java:136) at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:106) at org.mvel2.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:49) at org.mvel2.MVEL.eval(MVEL.java:408) at org.mvel2.ast.IfNode.getReducedValue(IfNode.java:89) at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:106) at org.mvel2.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:49) at org.mvel2.MVEL.eval(MVEL.java:165) at com.nucleus.rules.service.MvelTest.main(MvelTest.java:34) Caused by: java.lang.NullPointerException at org.mvel2.optimizers.impl.refl.nodes.NullSafe$1.getValue(NullSafe.java:39) at org.mvel2.optimizers.impl.refl.nodes.NullSafe.getValue(NullSafe.java:54) at org.mvel2.optimizers.impl.refl.nodes.GetterAccessor.getValue(GetterAccessor.java:40) ... 16 more
它在2.0版本中为我工作。 我在2或3位置尝试过甚至为空的抛出exception
我附加了例外
Exception in thread "main" [Error: cannot invoke getter: getChild [declr.class: Student; act.class: Student]] [Near : {... ame ;}}} else { return "Noo" } ....}] [Line: 1, Column: 218] at org.mvel.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:156) at org.mvel.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:54) at org.mvel.MVEL.eval(MVEL.java:124) at MvelTest.main(MvelTest.java:33) Caused by: [Error: cannot invoke getter: getChild [declr.class: Student; act.class: Student]] [Near : {... loopVariable0.?child.?name ;} ....}] [Line: 1, Column: 143] at org.mvel.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:156) at org.mvel.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:54) at org.mvel.MVEL.eval(MVEL.java:107) at org.mvel.ast.IfNode.getReducedValue(IfNode.java:64) at org.mvel.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:106) ... 3 more Caused by: [Error: cannot invoke getter: getChild [declr.class: Student; act.class: Student]] [Near : {... Unknown ....}] at org.mvel.optimizers.impl.refl.GetterAccessor.getValue(GetterAccessor.java:51) at org.mvel.optimizers.impl.refl.VariableAccessor.getValue(VariableAccessor.java:38) at org.mvel.optimizers.dynamic.DynamicGetAccessor.getValue(DynamicGetAccessor.java:44) at org.mvel.ast.ASTNode.getReducedValueAccelerated(ASTNode.java:97) at org.mvel.ast.BinaryOperation.getReducedValueAccelerated(BinaryOperation.java:64) at org.mvel.compiler.ExecutableAccessor.getValue(ExecutableAccessor.java:46) at org.mvel.ast.IfNode.getReducedValueAccelerated(IfNode.java:48) at org.mvel.compiler.ExecutableAccessor.getValue(ExecutableAccessor.java:46) at org.mvel.ast.ForEachNode.getReducedValue(ForEachNode.java:148) at org.mvel.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:106) ... 7 more Caused by: [Error: cannot invoke getter: getAge [declr.class: Child; act.class: null]] [Near : {... Unknown ....}] at org.mvel.optimizers.impl.refl.GetterAccessor.getValue(GetterAccessor.java:51) at org.mvel.optimizers.impl.refl.GetterAccessor.getValue(GetterAccessor.java:38) ... 16 more Caused by: java.lang.NullPointerException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:483) at org.mvel.optimizers.impl.refl.GetterAccessor.getValue(GetterAccessor.java:41) ... 17 more