[英]java.lang.VerifyError thrown when creating a method using JavaAssist
我试图使用JavaAssist版本3.12.1.GA来执行使用Java 8实现接口的Pojo的某些运行时代码生成。尝试创建具有Object返回类型的方法时遇到错误。
错误:
Caused by: java.lang.VerifyError: (class: person, method: getColumnByIndex signature: (I)Ljava/lang/Object;) Wrong return type in function
添加getColumnByIndex
方法时被抛出。
这是完整的示例类:
public class Example {
public interface Domain {
public int getIdentifier();
public Object getColumnByIndex(int i);
}
public static void main(final String[] args) throws NotFoundException, CannotCompileException, InstantiationException, IllegalAccessException {
final ClassPool pool = ClassPool.getDefault();
final CtClass cc = pool.makeClass("Person");
cc.addInterface(resolveCtClass(Domain.class));
final CtField idField = new CtField(CtClass.intType, "id", cc);
final CtMethod idGetter = CtNewMethod.getter("getId", idField);
final CtMethod idSetter = CtNewMethod.setter("setId", idField);
cc.addField(idField);
cc.addMethod(idGetter);
cc.addMethod(idSetter);
final CtField firstNameField = new CtField(resolveCtClass(String.class), "firstName", cc);
final CtMethod firstNameGetter = CtNewMethod.getter("getFirstName", firstNameField);
final CtMethod firstNameSetter = CtNewMethod.setter("setFirstName", firstNameField);
cc.addField(firstNameField);
cc.addMethod(firstNameSetter);
cc.addMethod(firstNameGetter);
final CtMethod getIdentifier = CtNewMethod.make("public int getIdentifier () { return id; }", cc);
cc.addMethod(getIdentifier);
final CtMethod getColumnByIndex = CtNewMethod.make(
"public Object getColumnByIndex(int i) {"
+ "switch (i) {"
+ "case 0:"
+ "return id;"
+ "case 1:"
+ "return firstName;"
+ "default: "
+ "throw new IllegalArgumentException(\"Tried getting column index i, but this column index does not exist\");"
+ "}"
+ "}", cc);
cc.addMethod(getColumnByIndex);
final Class<?> dynamicClass = cc.toClass();
final Domain domainImpl = (Domain) dynamicClass.newInstance();
System.out.println(domainImpl.getIdentifier());
System.out.println(domainImpl.getColumnByIndex(0));
}
private static CtClass resolveCtClass(final Class<?> clazz) throws NotFoundException {
final ClassPool pool = ClassPool.getDefault();
return pool.get(clazz.getName());
}
如何解决java.lang.VeryifyError?
显然, int
类型的id
字段不会自动装箱到Integer
,因此您可以手动执行:
switch (i) {
case 0: return Integer.valueOf(id);
case 1: return firstName;
default: throw new IllegalArgumentException("...");
}
或者将所有内容都转换为Integer
,包括Domain.getIdentifier()
的返回类型。 Java中的原始类型不是Object
的! 存在包装程序类型以伪造JVM中的单个根层次结构,并且编译器在适当时静默插入诸如Integer.valueOf(int)
和Integer.intValue()
类的调用,但是有时抽象泄漏给用户。
由于您正在编写的代码似乎是数据库访问的东西,因此,我宁愿使用第二种选择,以便所有内容都可以为空-否则,要表示要插入的记录,您将不得不依赖一些零进制值(如零) ,-1或其他值。
可运行的要点
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