Package org.springframework.beans

Class BeanUtils

java.lang.Object
org.springframework.beans.BeanUtils
public abstract class BeanUtils extends Object
Static convenience methods for JavaBeans: for instantiating beans, checking bean property types, copying bean properties, etc.

Mainly for internal use within the framework, but to some degree also useful for application classes. Consider Apache Commons BeanUtils, BULL - Bean Utils Light Library, or similar third-party frameworks for more comprehensive bean utilities.

Author:
Rod Johnson, Juergen Hoeller, Rob Harrop, Sam Brannen, Sebastien Deleuze

  • Constructor Details

    • BeanUtils

      public BeanUtils()

  • Method Details

    • instantiate

      @Deprecated public static <T> T instantiate(Class<T> clazz) throws BeanInstantiationException
      Deprecated.
      as of Spring 5.0, following the deprecation of Class.newInstance() in JDK 9
      Convenience method to instantiate a class using its no-arg constructor.
      Parameters:
      clazz - class to instantiate
      Returns:
      the new instance
      Throws:
      BeanInstantiationException - if the bean cannot be instantiated
      See Also:

    • instantiateClass

      public static <T> T instantiateClass(Class<T> clazz) throws BeanInstantiationException
      Instantiate a class using its 'primary' constructor (for Kotlin classes, potentially having default arguments declared) or its default constructor (for regular Java classes, expecting a standard no-arg setup).

      Note that this method tries to set the constructor accessible if given a non-accessible (that is, non-public) constructor.

      Parameters:
      clazz - the class to instantiate
      Returns:
      the new instance
      Throws:
      BeanInstantiationException - if the bean cannot be instantiated. The cause may notably indicate a NoSuchMethodException if no primary/default constructor was found, a NoClassDefFoundError or other LinkageError in case of an unresolvable class definition (e.g. due to a missing dependency at runtime), or an exception thrown from the constructor invocation itself.
      See Also:

    • instantiateClass

      public static <T> T instantiateClass(Class<?> clazz, Class<T> assignableTo) throws BeanInstantiationException
      Instantiate a class using its no-arg constructor and return the new instance as the specified assignable type.

      Useful in cases where the type of the class to instantiate (clazz) is not available, but the type desired (assignableTo) is known.

      Note that this method tries to set the constructor accessible if given a non-accessible (that is, non-public) constructor.

      Parameters:
      clazz - class to instantiate
      assignableTo - type that clazz must be assignableTo
      Returns:
      the new instance
      Throws:
      BeanInstantiationException - if the bean cannot be instantiated
      See Also:

    • instantiateClass

      public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException
      Convenience method to instantiate a class using the given constructor.

      Note that this method tries to set the constructor accessible if given a non-accessible (that is, non-public) constructor, and supports Kotlin classes with optional parameters and default values.

      Parameters:
      ctor - the constructor to instantiate
      args - the constructor arguments to apply (use null for an unspecified parameter, Kotlin optional parameters and Java primitive types are supported)
      Returns:
      the new instance
      Throws:
      BeanInstantiationException - if the bean cannot be instantiated
      See Also:

    • getResolvableConstructor

      public static <T> Constructor<T> getResolvableConstructor(Class<T> clazz)
      Return a resolvable constructor for the provided class, either a primary or single public constructor with arguments, or a single non-public constructor with arguments, or simply a default constructor. Callers have to be prepared to resolve arguments for the returned constructor's parameters, if any.
      Parameters:
      clazz - the class to check
      Throws:
      IllegalStateException - in case of no unique constructor found at all
      Since:
      5.3
      See Also:

    • findPrimaryConstructor

      @Nullable public static <T> Constructor<T> findPrimaryConstructor(Class<T> clazz)
      Return the primary constructor of the provided class. For Kotlin classes, this returns the Java constructor corresponding to the Kotlin primary constructor (as defined in the Kotlin specification). Otherwise, in particular for non-Kotlin classes, this simply returns null.
      Parameters:
      clazz - the class to check
      Since:
      5.0
      See Also:

    • findMethod

      @Nullable public static Method findMethod(Class<?> clazz, String methodName, Class<?>... paramTypes)
      Find a method with the given method name and the given parameter types, declared on the given class or one of its superclasses. Prefers public methods, but will return a protected, package access, or private method too.

      Checks Class.getMethod first, falling back to findDeclaredMethod. This allows to find public methods without issues even in environments with restricted Java security settings.

      Parameters:
      clazz - the class to check
      methodName - the name of the method to find
      paramTypes - the parameter types of the method to find
      Returns:
      the Method object, or null if not found
      See Also:

    • findDeclaredMethod

      @Nullable public static Method findDeclaredMethod(Class<?> clazz, String methodName, Class<?>... paramTypes)
      Find a method with the given method name and the given parameter types, declared on the given class or one of its superclasses. Will return a public, protected, package access, or private method.

      Checks Class.getDeclaredMethod, cascading upwards to all superclasses.

      Parameters:
      clazz - the class to check
      methodName - the name of the method to find
      paramTypes - the parameter types of the method to find
      Returns:
      the Method object, or null if not found
      See Also:

    • findMethodWithMinimalParameters

      @Nullable public static Method findMethodWithMinimalParameters(Class<?> clazz, String methodName) throws IllegalArgumentException
      Find a method with the given method name and minimal parameters (best case: none), declared on the given class or one of its superclasses. Prefers public methods, but will return a protected, package access, or private method too.

      Checks Class.getMethods first, falling back to findDeclaredMethodWithMinimalParameters. This allows for finding public methods without issues even in environments with restricted Java security settings.

      Parameters:
      clazz - the class to check
      methodName - the name of the method to find
      Returns:
      the Method object, or null if not found
      Throws:
      IllegalArgumentException - if methods of the given name were found but could not be resolved to a unique method with minimal parameters
      See Also:

    • findDeclaredMethodWithMinimalParameters

      @Nullable public static Method findDeclaredMethodWithMinimalParameters(Class<?> clazz, String methodName) throws IllegalArgumentException
      Find a method with the given method name and minimal parameters (best case: none), declared on the given class or one of its superclasses. Will return a public, protected, package access, or private method.

      Checks Class.getDeclaredMethods, cascading upwards to all superclasses.

      Parameters:
      clazz - the class to check
      methodName - the name of the method to find
      Returns:
      the Method object, or null if not found
      Throws:
      IllegalArgumentException - if methods of the given name were found but could not be resolved to a unique method with minimal parameters
      See Also:

    • findMethodWithMinimalParameters

      @Nullable public static Method findMethodWithMinimalParameters(Method[] methods, String methodName) throws IllegalArgumentException
      Find a method with the given method name and minimal parameters (best case: none) in the given list of methods.
      Parameters:
      methods - the methods to check
      methodName - the name of the method to find
      Returns:
      the Method object, or null if not found
      Throws:
      IllegalArgumentException - if methods of the given name were found but could not be resolved to a unique method with minimal parameters

    • resolveSignature

      @Nullable public static Method resolveSignature(String signature, Class<?> clazz)
      Parse a method signature in the form methodName[([arg_list])], where arg_list is an optional, comma-separated list of fully-qualified type names, and attempts to resolve that signature against the supplied Class.

      When not supplying an argument list (methodName) the method whose name matches and has the least number of parameters will be returned. When supplying an argument type list, only the method whose name and argument types match will be returned.

      Note then that methodName and methodName() are not resolved in the same way. The signature methodName means the method called methodName with the least number of arguments, whereas methodName() means the method called methodName with exactly 0 arguments.

      If no method can be found, then null is returned.

      Parameters:
      signature - the method signature as String representation
      clazz - the class to resolve the method signature against
      Returns:
      the resolved Method
      See Also:

    • getPropertyDescriptors

      public static PropertyDescriptor[] getPropertyDescriptors(Class<?> clazz) throws BeansException
      Retrieve the JavaBeans PropertyDescriptors of a given class.
      Parameters:
      clazz - the Class to retrieve the PropertyDescriptors for
      Returns:
      an array of PropertyDescriptors for the given class
      Throws:
      BeansException - if PropertyDescriptor look fails

    • getPropertyDescriptor

      @Nullable public static PropertyDescriptor getPropertyDescriptor(Class<?> clazz, String propertyName) throws BeansException
      Retrieve the JavaBeans PropertyDescriptors for the given property.
      Parameters:
      clazz - the Class to retrieve the PropertyDescriptor for
      propertyName - the name of the property
      Returns:
      the corresponding PropertyDescriptor, or null if none
      Throws:
      BeansException - if PropertyDescriptor lookup fails

    • findPropertyForMethod

      @Nullable public static PropertyDescriptor findPropertyForMethod(Method method) throws BeansException
      Find a JavaBeans PropertyDescriptor for the given method, with the method either being the read method or the write method for that bean property.
      Parameters:
      method - the method to find a corresponding PropertyDescriptor for, introspecting its declaring class
      Returns:
      the corresponding PropertyDescriptor, or null if none
      Throws:
      BeansException - if PropertyDescriptor lookup fails

    • findPropertyForMethod

      @Nullable public static PropertyDescriptor findPropertyForMethod(Method method, Class<?> clazz) throws BeansException
      Find a JavaBeans PropertyDescriptor for the given method, with the method either being the read method or the write method for that bean property.
      Parameters:
      method - the method to find a corresponding PropertyDescriptor for
      clazz - the (most specific) class to introspect for descriptors
      Returns:
      the corresponding PropertyDescriptor, or null if none
      Throws:
      BeansException - if PropertyDescriptor lookup fails
      Since:
      3.2.13

    • findEditorByConvention

      @Nullable public static PropertyEditor findEditorByConvention(@Nullable Class<?> targetType)
      Find a JavaBeans PropertyEditor following the 'Editor' suffix convention (e.g. "mypackage.MyDomainClass" → "mypackage.MyDomainClassEditor").

      Compatible to the standard JavaBeans convention as implemented by PropertyEditorManager but isolated from the latter's registered default editors for primitive types.

      Parameters:
      targetType - the type to find an editor for
      Returns:
      the corresponding editor, or null if none found

    • findPropertyType

      public static Class<?> findPropertyType(String propertyName, @Nullable Class<?>... beanClasses)
      Determine the bean property type for the given property from the given classes/interfaces, if possible.
      Parameters:
      propertyName - the name of the bean property
      beanClasses - the classes to check against
      Returns:
      the property type, or Object.class as fallback

    • getWriteMethodParameter

      public static MethodParameter getWriteMethodParameter(PropertyDescriptor pd)
      Obtain a new MethodParameter object for the write method of the specified property.
      Parameters:
      pd - the PropertyDescriptor for the property
      Returns:
      a corresponding MethodParameter object

    • getParameterNames

      public static String[] getParameterNames(Constructor<?> ctor)
      Determine required parameter names for the given constructor, considering the JavaBeans ConstructorProperties annotation as well as Spring's DefaultParameterNameDiscoverer.
      Parameters:
      ctor - the constructor to find parameter names for
      Returns:
      the parameter names (matching the constructor's parameter count)
      Throws:
      IllegalStateException - if the parameter names are not resolvable
      Since:
      5.3
      See Also:

    • isSimpleProperty

      public static boolean isSimpleProperty(Class<?> type)
      Check if the given type represents a "simple" property: a simple value type or an array of simple value types.

      See isSimpleValueType(Class) for the definition of simple value type.

      Used to determine properties to check for a "simple" dependency-check.

      Parameters:
      type - the type to check
      Returns:
      whether the given type represents a "simple" property
      See Also:

    • isSimpleValueType

      public static boolean isSimpleValueType(Class<?> type)
      Check if the given type represents a "simple" value type: a primitive or primitive wrapper, an enum, a String or other CharSequence, a Number, a Date, a Temporal, a URI, a URL, a Locale, or a Class.

      Void and void are not considered simple value types.

      Parameters:
      type - the type to check
      Returns:
      whether the given type represents a "simple" value type
      See Also:

    • copyProperties

      public static void copyProperties(Object source, Object target) throws BeansException
      Copy the property values of the given source bean into the target bean.

      Note: The source and target classes do not have to match or even be derived from each other, as long as the properties match. Any bean properties that the source bean exposes but the target bean does not will silently be ignored.

      This is just a convenience method. For more complex transfer needs, consider using a full BeanWrapper.

      As of Spring Framework 5.3, this method honors generic type information when matching properties in the source and target objects.

      The following table provides a non-exhaustive set of examples of source and target property types that can be copied as well as source and target property types that cannot be copied.

      source property typetarget property typecopy supported
      IntegerIntegeryes
      IntegerNumberyes
      List<Integer>List<Integer>yes
      List<?>List<?>yes
      List<Integer>List<?>yes
      List<Integer>List<? extends Number>yes
      StringIntegerno
      NumberIntegerno
      List<Integer>List<Long>no
      List<Integer>List<Number>no
      Parameters:
      source - the source bean
      target - the target bean
      Throws:
      BeansException - if the copying failed
      See Also:

    • copyProperties

      public static void copyProperties(Object source, Object target, Class<?> editable) throws BeansException
      Copy the property values of the given source bean into the given target bean, only setting properties defined in the given "editable" class (or interface).

      Note: The source and target classes do not have to match or even be derived from each other, as long as the properties match. Any bean properties that the source bean exposes but the target bean does not will silently be ignored.

      This is just a convenience method. For more complex transfer needs, consider using a full BeanWrapper.

      As of Spring Framework 5.3, this method honors generic type information when matching properties in the source and target objects. See the documentation for copyProperties(Object, Object) for details.

      Parameters:
      source - the source bean
      target - the target bean
      editable - the class (or interface) to restrict property setting to
      Throws:
      BeansException - if the copying failed
      See Also:

    • copyProperties

      public static void copyProperties(Object source, Object target, String... ignoreProperties) throws BeansException
      Copy the property values of the given source bean into the given target bean, ignoring the given "ignoreProperties".

      Note: The source and target classes do not have to match or even be derived from each other, as long as the properties match. Any bean properties that the source bean exposes but the target bean does not will silently be ignored.

      This is just a convenience method. For more complex transfer needs, consider using a full BeanWrapper.

      As of Spring Framework 5.3, this method honors generic type information when matching properties in the source and target objects. See the documentation for copyProperties(Object, Object) for details.

      Parameters:
      source - the source bean
      target - the target bean
      ignoreProperties - array of property names to ignore
      Throws:
      BeansException - if the copying failed
      See Also: