Class ClassInspector

java.lang.Object
org.apache.derby.iapi.services.loader.ClassInspector

public class ClassInspector extends Object
Methods to find out relationships between classes and methods within a class. All class names within this interface are treated as java language class names, e.g. int, COM.foo.Myclass, int[], java.lang.Object[]. That is java internal class names as defined in the class file format are not understood.
  • Field Details

  • Constructor Details

    • ClassInspector

      public ClassInspector(ClassFactory cf)
      DO NOT USE! use the method in ClassFactory.
  • Method Details

    • instanceOf

      public boolean instanceOf(String className, Object obj) throws ClassNotFoundException
      Is the given object an instance of the named class?
      Parameters:
      className - The name of the class
      obj - The object to test to see if it's an instance of the named class
      Returns:
      true if obj is an instanceof className, false if not
      Throws:
      ClassNotFoundException
    • assignableTo

      public boolean assignableTo(String fromClassName, String toClassName)
      Is one named class assignable to another named class or interface?
      Parameters:
      fromClassName - The name of the class to be assigned
      toClassName - The name of the class to be assigned to
      Returns:
      true if an object of type fromClass can be assigned to an object of type toClass, false if not.
    • accessible

      public boolean accessible(String className) throws ClassNotFoundException
      Does the named class exist, and is it accessible?
      Parameters:
      className - The name of the class to test for existence
      Returns:
      true if the class exists and is accessible, false if not
      Throws:
      ClassNotFoundException
    • getType

      public String getType(Member member)
      Get the Java name of the return type from a Member representing a method or the type of a Member representing a field.
      Parameters:
      member - A Member representing the method for which we want the return type.
      Returns:
      A Java-language-style string describing the return type of the method (for example, it returns "int" instead of "I".
    • findPublicMethod

      public Member findPublicMethod(String receiverType, String methodName, String[] parmTypes, String[] primParmTypes, boolean[] isParam, boolean staticMethod, boolean repeatLastParameter, boolean hasVarargs) throws ClassNotFoundException, StandardException
      Find a public method that implements a given signature. The signature is given using the full Java class names of the types.
      A untyped null parameter is indicated by passing in an empty string ("") as its class name.
      If receiverType represents an interface then the methods of java.lang.Object are included in the candidate list.
      If the caller is simply checking to see that a public method with the specified name exists, regardless of the signature, exists, then the caller should pass in a null for parmTypes. (This is useful for checking the validity of a method alias when creating one.)
      We use a two-pass algorithm to resolve methods. In the first pass, we use all "object" types to try to match a method. If this fails, in the second pass, an array of "primitive" types (if the parameter has one, otherwise the same object type is used) is passed in, as well as the "object" type array. For each parameter of a method, we try to match it against either the "object" type, or the "primitive" type. Of all the qualified candidate methods found, we choose the closest one to the input parameter types. This involves comparing methods whose parameters are mixed "object" and "primitive" types in the second pass. This is eventually handled in classConvertableFromTo.
      Parameters:
      receiverType - The class name of the receiver
      methodName - The name of the method
      parmTypes - An array of class names representing the parameter types. Pass a zero-element array if there are no parameters. Pass a null if it is okay to match any signature.
      primParmTypes - This is used in the second pass of the two-pass method resolution algorithm. Use primitive type if it has one, otherwise use same object type
      isParam - Array of booleans telling whether parameter is a ?.
      staticMethod - Find a static method.
      repeatLastParameter - If true the last parameter may be repeated any number of times (total count must be greater than one). If false the last parameter is matched as usual. This also requires an exact match on the last parameter type.
      Returns:
      A Member representing the matching method. Returns null if no such method.
      Throws:
      ClassNotFoundException - One or more of the classes does not exist.
      StandardException - Thrown on ambiguous method invocation.
      See Also:
    • findPublicField

      public Member findPublicField(String receiverType, String fieldName, boolean staticField) throws StandardException
      Find a public field for a class. This follows the semantics of the java compiler for locating a field. This means if a field fieldName exists in the class with package, private or protected then an error is raised. Even if the field hides a field fieldName in a super-class/super--interface. See the JVM spec on fields.
      Parameters:
      receiverType - The class name of the receiver
      fieldName - The name of the field
      staticField - Find a static field
      Returns:
      A Member representing the matching field.
      Throws:
      StandardException - Class or field does not exist or is not public or a security exception.
      See Also:
    • findPublicConstructor

      public Member findPublicConstructor(String receiverType, String[] parmTypes, String[] primParmTypes, boolean[] isParam) throws ClassNotFoundException, StandardException
      Find a public constructor that implements a given signature. The signature is given using the full Java class names of the types.
      A untyped null parameter is indicated by passing in an empty string ("") as its class name.
      Parameters:
      receiverType - The class name of the receiver
      parmTypes - An array of class names representing the parameter types. Pass a zero-element array if there are no parameters.
      primParmTypes - This is used in the second pass of the two-pass method resolution algorithm. Use primitive type if it has one, otherwise use same object type
      isParam - Array of booleans telling whether parameter is a ?.
      Returns:
      A Member representing the matching constructor. Returns null if no such constructor.
      Throws:
      ClassNotFoundException - One or more of the classes does not exist.
      StandardException - Thrown on ambiguous constructor invocation.
      See Also:
    • getTypeBounds

      public Class[][] getTypeBounds(Class parameterizedInterface, Class implementation) throws StandardException
      Given an implementation of a parameterized interface, return the bounds on the type variables. May return null if type resolution fails.
      Throws:
      StandardException
    • isVarArgsMethod

      public boolean isVarArgsMethod(Member member)
      Return true if the method or constructor supports varargs.
    • getGenericParameterTypes

      public Class<?>[] getGenericParameterTypes(Class parameterizedType, Class implementation) throws StandardException
      Given an implementation of a parameterized interface, return the actual types of the interface type variables. May return null or an array of nulls if type resolution fails.
      Throws:
      StandardException
    • getParameterTypes

      public String[] getParameterTypes(Member method)
      Get the parameter types for a method described by a Member as a String[].
      Parameters:
      method - A Member describing a method
      Returns:
      A String[] describing the parameters of the method
    • primitiveType

      public static boolean primitiveType(String typeName)
      Determine whether a type is a Java primitive, like int or boolean
      Parameters:
      typeName - The name of the Java type
      Returns:
      true if it's a primitive type
    • resolveMethod

      private Member resolveMethod(Class receiverClass, String methodName, Class[] paramClasses, Class[] primParamClasses, boolean[] isParam, boolean staticMethod, boolean repeatLastParameter, Member[] methods, boolean hasVarargs) throws StandardException
      Tricky function to resolve a method. If primParamClasses is null we know it's first pass. First pass try to match as all "object" types, second pass try to match any combination of "object" and "primitive" types. Find the closest match among all the qualified candidates. If there's a tie, it's ambiguous. The preceding paragraph is a bit misleading. As of release 10.4, the second pass did not consider arbitrary combinations of primitive and wrapper types. This is because the first pass removed from consideration candidates which would be allowed under ANSI rules. As a fix for bug DERBY-3652, we now allow primitive and wrapper type matches during the first pass. The ANSI rules are documented in DERBY-3652.
      Parameters:
      receiverClass - the class who holds the methods
      methodName - the name of method
      paramClasses - object type classes of input parameters
      primParamClasses - primitive type classes or null
      isParam - isParam (for ?) array
      staticMethod - static method or not
      methods - method stack
      Returns:
      the matched method
      Throws:
      StandardException
    • getClass

      public Class<?> getClass(String className) throws ClassNotFoundException
      Get (load) the class for the given class name. This method converts any java language class name into a Class object. This includes cases like String[] and primitive types. This will attempt to load the class from the application set.
      Throws:
      ClassNotFoundException - Class cannot be found, or a SecurityException or LinkageException was thrown loading the class.
    • signatureConvertableFromTo

      private boolean signatureConvertableFromTo(Class[] fromTypes, Class[] primFromTypes, Class[] toTypes, boolean[] isParam, boolean mixTypes)
      Can we convert a signature from fromTypes(primFromTypes) to toTypes. "mixTypes" is a flag to show if object/primitive type conversion is possible; this is used for comparing two candidate methods in the second pass of the two pass method resolution.
      Parameters:
      fromTypes - from types' classes
      primFromTypes - primitive from types or null
      toTypes - to types' classes
      isParam - is parameter (?) or not
      mixTypes - mixing object/primitive types for comparison
    • classConvertableFromTo

      protected boolean classConvertableFromTo(Class fromClass, Class toClass, boolean mixTypes)
      Can we convert a fromClass to toClass. "mixTypes" is a flag to show if object/primitive type conversion is possible; this is used for comparing two candidate methods in the second pass of the two pass method resolution.
      Parameters:
      fromClass - from class
      toClass - to class
      mixTypes - mixing object/primitive types for comparison
    • readableClassName

      public static String readableClassName(Class clazz)
      Translate a JVM-style type descriptor to a Java-language-style type name.
      Parameters:
      clazz - The String that contains the JVM type name
      Returns:
      The Java-language-style type name
    • getDeclaringClass

      public String getDeclaringClass(Member method)
      Get the declaring class for a method.
      Parameters:
      method - A Member describing a method
      Returns:
      A String with the declaring class
      See Also:
    • findTypeBounds

      private Class[][] findTypeBounds(ParameterizedType pt)
      Get the type bounds for all of the type variables of the given parameterized type.
    • boundType

      private Class[] boundType(Type type)
      Get the bounds for a single type variable.
    • getRawType

      private Class getRawType(Type bound)
      Get the raw type of a type bound.
    • getTypeChain

      private ArrayList<Class<?>> getTypeChain(Class<?> chainEnd, Class<?> start)
      Construct an inheritance chain of types stretching from a supertype down to a concrete implementation.
    • getResolvedTypes

      private HashMap<Type,Type> getResolvedTypes(ArrayList<Class<?>> chain)
      Given an inheritance chain of types, stretching from a superclass down to a terminal concrete class, construct a map of generic types to their resolved types.
    • addResolvedTypes

      private void addResolvedTypes(HashMap<Type,Type> resolvedTypes, Type genericType)
      Given a generic type, add its parameter types to an evolving map of resolved types. Some of the resolved types may be generic type variables which will need further resolution from other generic types.
    • getParameterTypes

      private ArrayList<Class<?>> getParameterTypes(Class<?> parameterizedType, HashMap<Type,Type> resolvedTypes)
      Given a map of resolved types, compose them together in order to resolve the actual concrete types that are plugged into the parameterized type.