我正在尝试使用 javassist 生成我的实体类。一切都很顺利,直到我将 GeneratedValue 注释添加到 Id 字段。@Id 注释工作正常,但是当我添加 @GeneeratedValue 时出现异常。这是我的代码:
ClassPool cp = ClassPool.getDefault();
CtClass ctClass = cp.makeClass("test.Snake");
ClassFile classFile = ctClass.getClassFile();
classFile.setVersionToJava5();
AnnotationsAttribute attribute = new AnnotationsAttribute(classFile.getConstPool(), AnnotationsAttribute.visibleTag);
Annotation idAnnotation = new Annotation(classFile.getConstPool(), ClassPool.getDefault().get("javax.persistence.Id"));
attribute.addAnnotation(idAnnotation);
Annotation gvAnnotation = new Annotation(classFile.getConstPool(), ClassPool.getDefault().get("javax.persistence.GeneratedValue"));
attribute.addAnnotation(gvAnnotation);
CtField idField = new CtField(ClassPool.getDefault().get("java.lang.Long"), "id", ctClass);
idField.getFieldInfo().addAttribute(attribute);
ctClass.addField(idField);
CtField nameField = new CtField(ClassPool.getDefault().get("java.lang.String"), "name", ctClass);
ctClass.addField(nameField);
AnnotationsAttribute attr = new AnnotationsAttribute(classFile.getConstPool(), AnnotationsAttribute.visibleTag);
Annotation annotation = new Annotation(classFile.getConstPool(), ClassPool.getDefault().get("javax.persistence.Entity"));
attr.addAnnotation(annotation);
classFile.addAttribute(attr);
snakeClass = ctClass.toClass();
newInstance = snakeClass.newInstance();
这是我得到的例外:
java.lang.NullPointerException
at javassist.bytecode.ConstPool.getUtf8Info(ConstPool.java:565)
at javassist.bytecode.annotation.EnumMemberValue.getValue(EnumMemberValue.java:98)
at javassist.bytecode.annotation.EnumMemberValue.write(EnumMemberValue.java:116)
at javassist.bytecode.annotation.Annotation.write(Annotation.java:316)
at javassist.bytecode.AnnotationsAttribute.setAnnotations(AnnotationsAttribute.java:246)
at javassist.bytecode.AnnotationsAttribute.addAnnotation(AnnotationsAttribute.java:211)
at ClassLoadingTest.javassitTest(ClassLoadingTest.java:56)
@GeneratedValue 似乎有问题。当我在没有 id 的情况下单独使用它时,我也会得到这个异常。当我使用 eclipse 调试器观察变量值时,我得到了这个
com.sun.jdi.InvocationException occurred invoking method.
而不是注释值。但对于 Id 注释,它显示一个 javassist 注释对象。
我是 javassist 的新手。谁能帮我?