org.apache.commons.lang3.builder

## Class ReflectionToStringBuilder

- java.lang.Object
- - org.apache.commons.lang3.builder.ToStringBuilder
  - - org.apache.commons.lang3.builder.ReflectionToStringBuilder

- All Implemented Interfaces:
    Builder<String>

      public class ReflectionToStringBuilder
      extends ToStringBuilder

  Assists in implementing `Object.toString()` methods using reflection.

  This class uses reflection to determine the fields to append. Because these fields are usually private, the class uses `AccessibleObject.setAccessible(java.lang.reflect.AccessibleObject[], boolean)` to change the visibility of the fields. This will fail under a security manager, unless the appropriate permissions are set up correctly.

  Using reflection to access (private) fields circumvents any synchronization protection guarding access to these fields. If a toString method cannot safely read a field, you should exclude it from the toString method, or use synchronization consistent with the class' lock management around the invocation of the method. Take special care to exclude non-thread-safe collection classes, because these classes may throw ConcurrentModificationException if modified while the toString method is executing.

  A typical invocation for this method would look like:

       public String toString() {
           return ReflectionToStringBuilder.toString(this);
       }

  You can also use the builder to debug 3rd party objects:

       System.out.println("An object: " + ReflectionToStringBuilder.toString(anObject));

  A subclass can control field output by overriding the methods:

  - `accept(java.lang.reflect.Field)`
  - `getValue(java.lang.reflect.Field)`

  For example, this method does not include the `password` field in the returned `String`:

       public String toString() {
           return (new ReflectionToStringBuilder(this) {
               protected boolean accept(Field f) {
                   return super.accept(f) && !f.getName().equals("password");
               }
           }).toString();
       }

  The exact format of the `toString` is determined by the `ToStringStyle` passed into the constructor.

  Note: the default `ToStringStyle` will only do a "shallow" formatting, i.e. composed objects are not further traversed. To get "deep" formatting, use an instance of `RecursiveToStringStyle`.

  Since:
    2.0
  Version:
    $Id: ReflectionToStringBuilder.java 1583482 2014-03-31 22:54:57Z niallp $

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected String[]` | `excludeFieldNames` Which field names to exclude from output.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `ReflectionToStringBuilder(Object object)` Constructor.
    `ReflectionToStringBuilder(Object object, ToStringStyle style)` Constructor.
    `ReflectionToStringBuilder(Object object, ToStringStyle style, StringBuffer buffer)` Constructor.
    `ReflectionToStringBuilder(T object, ToStringStyle style, StringBuffer buffer, Class<? super T> reflectUpToClass, boolean outputTransients, boolean outputStatics)` Constructor.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected boolean` | `accept(Field field)` Returns whether or not to append the given `Field`.
    `protected void` | `appendFieldsIn(Class<?> clazz)` Appends the fields and values defined by the given object of the given Class.
    `String[]` | `getExcludeFieldNames()`
    `Class<?>` | `getUpToClass()` Gets the last super class to stop appending fields for.
    `protected Object` | `getValue(Field field)` Calls `java.lang.reflect.Field.get(Object)`.
    `boolean` | `isAppendStatics()` Gets whether or not to append static fields.
    `boolean` | `isAppendTransients()` Gets whether or not to append transient fields.
    `ReflectionToStringBuilder` | `reflectionAppendArray(Object array)` Append to the `toString` an `Object` array.
    `void` | `setAppendStatics(boolean appendStatics)` Sets whether or not to append static fields.
    `void` | `setAppendTransients(boolean appendTransients)` Sets whether or not to append transient fields.
    `ReflectionToStringBuilder` | `setExcludeFieldNames(String... excludeFieldNamesParam)` Sets the field names to exclude.
    `void` | `setUpToClass(Class<?> clazz)` Sets the last super class to stop appending fields for.
    `String` | `toString()` Gets the String built by this builder.
    `static String` | `toString(Object object)` Builds a `toString` value using the default `ToStringStyle` through reflection.
    `static String` | `toString(Object object, ToStringStyle style)` Builds a `toString` value through reflection.
    `static String` | `toString(Object object, ToStringStyle style, boolean outputTransients)` Builds a `toString` value through reflection.
    `static String` | `toString(Object object, ToStringStyle style, boolean outputTransients, boolean outputStatics)` Builds a `toString` value through reflection.
    `static <T> String` | `toString(T object, ToStringStyle style, boolean outputTransients, boolean outputStatics, Class<? super T> reflectUpToClass)` Builds a `toString` value through reflection.
    `static String` | `toStringExclude(Object object, Collection<String> excludeFieldNames)` Builds a String for a toString method excluding the given field names.
    `static String` | `toStringExclude(Object object, String... excludeFieldNames)` Builds a String for a toString method excluding the given field names.

    - ### Methods inherited from class org.apache.commons.lang3.builder.ToStringBuilder

      `append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, append, appendAsObjectToString, appendSuper, appendToString, build, getDefaultStyle, getObject, getStringBuffer, getStyle, reflectionToString, reflectionToString, reflectionToString, reflectionToString, setDefaultStyle`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

- - ### Field Detail

    - #### excludeFieldNames

          protected String[] excludeFieldNames

      Which field names to exclude from output. Intended for fields like `"password"`.
      Since:
        3.0 this is protected instead of private

  - ### Constructor Detail

    - #### ReflectionToStringBuilder

          public ReflectionToStringBuilder(Object object)

      Constructor.

      This constructor outputs using the default style set with `setDefaultStyle`.

      Parameters:
        `object` - the Object to build a `toString` for, must not be `null`
      Throws:
        `IllegalArgumentException` - if the Object passed in is `null`

    - #### ReflectionToStringBuilder

          public ReflectionToStringBuilder(Object object,
                                   ToStringStyle style)

      Constructor.

      If the style is `null`, the default style is used.

      Parameters:
        `object` - the Object to build a `toString` for, must not be `null`
        `style` - the style of the `toString` to create, may be `null`
      Throws:
        `IllegalArgumentException` - if the Object passed in is `null`

    - #### ReflectionToStringBuilder

          public ReflectionToStringBuilder(Object object,
                                   ToStringStyle style,
                                   StringBuffer buffer)

      Constructor.

      If the style is `null`, the default style is used.

      If the buffer is `null`, a new one is created.

      Parameters:
        `object` - the Object to build a `toString` for
        `style` - the style of the `toString` to create, may be `null`
        `buffer` - the `StringBuffer` to populate, may be `null`
      Throws:
        `IllegalArgumentException` - if the Object passed in is `null`

    - #### ReflectionToStringBuilder

          public ReflectionToStringBuilder(T object,
                                   ToStringStyle style,
                                   StringBuffer buffer,
                                   Class<? super T> reflectUpToClass,
                                   boolean outputTransients,
                                   boolean outputStatics)

      Constructor.
      Type Parameters:
        `T` - the type of the object
      Parameters:
        `object` - the Object to build a `toString` for
        `style` - the style of the `toString` to create, may be `null`
        `buffer` - the `StringBuffer` to populate, may be `null`
        `reflectUpToClass` - the superclass to reflect up to (inclusive), may be `null`
        `outputTransients` - whether to include transient fields
        `outputStatics` - whether to include static fields
      Since:
        2.1

  - ### Method Detail

    - #### toString

          public static String toString(Object object)

      Builds a `toString` value using the default `ToStringStyle` through reflection.

      It uses `AccessibleObject.setAccessible` to gain access to private fields. This means that it will throw a security exception if run under a security manager, if the permissions are not set up correctly. It is also not as efficient as testing explicitly.

      Transient members will be not be included, as they are likely derived. Static fields will not be included. Superclass fields will be appended.

      Parameters:
        `object` - the Object to be output
      Returns:
        the String result
      Throws:
        `IllegalArgumentException` - if the Object is `null`

    - #### toString

          public static String toString(Object object,
                        ToStringStyle style)

      Builds a `toString` value through reflection.

      It uses `AccessibleObject.setAccessible` to gain access to private fields. This means that it will throw a security exception if run under a security manager, if the permissions are not set up correctly. It is also not as efficient as testing explicitly.

      Transient members will be not be included, as they are likely derived. Static fields will not be included. Superclass fields will be appended.

      If the style is `null`, the default `ToStringStyle` is used.

      Parameters:
        `object` - the Object to be output
        `style` - the style of the `toString` to create, may be `null`
      Returns:
        the String result
      Throws:
        `IllegalArgumentException` - if the Object or `ToStringStyle` is `null`

    - #### toString

          public static String toString(Object object,
                        ToStringStyle style,
                        boolean outputTransients)

      Builds a `toString` value through reflection.

      It uses `AccessibleObject.setAccessible` to gain access to private fields. This means that it will throw a security exception if run under a security manager, if the permissions are not set up correctly. It is also not as efficient as testing explicitly.

      If the `outputTransients` is `true`, transient members will be output, otherwise they are ignored, as they are likely derived fields, and not part of the value of the Object.

      Static fields will not be included. Superclass fields will be appended.

      If the style is `null`, the default `ToStringStyle` is used.

      Parameters:
        `object` - the Object to be output
        `style` - the style of the `toString` to create, may be `null`
        `outputTransients` - whether to include transient fields
      Returns:
        the String result
      Throws:
        `IllegalArgumentException` - if the Object is `null`

    - #### toString

          public static String toString(Object object,
                        ToStringStyle style,
                        boolean outputTransients,
                        boolean outputStatics)

      Builds a `toString` value through reflection.

      It uses `AccessibleObject.setAccessible` to gain access to private fields. This means that it will throw a security exception if run under a security manager, if the permissions are not set up correctly. It is also not as efficient as testing explicitly.

      If the `outputTransients` is `true`, transient fields will be output, otherwise they are ignored, as they are likely derived fields, and not part of the value of the Object.

      If the `outputStatics` is `true`, static fields will be output, otherwise they are ignored.

      Static fields will not be included. Superclass fields will be appended.

      If the style is `null`, the default `ToStringStyle` is used.

      Parameters:
        `object` - the Object to be output
        `style` - the style of the `toString` to create, may be `null`
        `outputTransients` - whether to include transient fields
        `outputStatics` - whether to include transient fields
      Returns:
        the String result
      Throws:
        `IllegalArgumentException` - if the Object is `null`
      Since:
        2.1

    - #### toString

          public static <T> String toString(T object,
                            ToStringStyle style,
                            boolean outputTransients,
                            boolean outputStatics,
                            Class<? super T> reflectUpToClass)

      Builds a `toString` value through reflection.

      It uses `AccessibleObject.setAccessible` to gain access to private fields. This means that it will throw a security exception if run under a security manager, if the permissions are not set up correctly. It is also not as efficient as testing explicitly.

      If the `outputTransients` is `true`, transient fields will be output, otherwise they are ignored, as they are likely derived fields, and not part of the value of the Object.

      If the `outputStatics` is `true`, static fields will be output, otherwise they are ignored.

      Superclass fields will be appended up to and including the specified superclass. A null superclass is treated as `java.lang.Object`.

      If the style is `null`, the default `ToStringStyle` is used.

      Type Parameters:
        `T` - the type of the object
      Parameters:
        `object` - the Object to be output
        `style` - the style of the `toString` to create, may be `null`
        `outputTransients` - whether to include transient fields
        `outputStatics` - whether to include static fields
        `reflectUpToClass` - the superclass to reflect up to (inclusive), may be `null`
      Returns:
        the String result
      Throws:
        `IllegalArgumentException` - if the Object is `null`
      Since:
        2.1

    - #### toStringExclude

          public static String toStringExclude(Object object,
                               Collection<String> excludeFieldNames)

      Builds a String for a toString method excluding the given field names.
      Parameters:
        `object` - The object to "toString".
        `excludeFieldNames` - The field names to exclude. Null excludes nothing.
      Returns:
        The toString value.

    - #### toStringExclude

          public static String toStringExclude(Object object,
                               String... excludeFieldNames)

      Builds a String for a toString method excluding the given field names.
      Parameters:
        `object` - The object to "toString".
        `excludeFieldNames` - The field names to exclude
      Returns:
        The toString value.

    - #### accept

          protected boolean accept(Field field)

      Returns whether or not to append the given `Field`.
      - Transient fields are appended only if `isAppendTransients()` returns `true`.
      - Static fields are appended only if `isAppendStatics()` returns `true`.
      - Inner class fields are not appended.
      Parameters:
        `field` - The Field to test.
      Returns:
        Whether or not to append the given `Field`.

    - #### appendFieldsIn

          protected void appendFieldsIn(Class<?> clazz)

      Appends the fields and values defined by the given object of the given Class.

      If a cycle is detected as an object is "toString()'ed", such an object is rendered as if `Object.toString()` had been called and not implemented by the object.

      Parameters:
        `clazz` - The class of object parameter

    - #### getExcludeFieldNames

          public String[] getExcludeFieldNames()

      Returns:
        Returns the excludeFieldNames.

    - #### getUpToClass

          public Class<?> getUpToClass()

      Gets the last super class to stop appending fields for.

      Returns:
        The last super class to stop appending fields for.

    - #### getValue

          protected Object getValue(Field field)
                             throws IllegalArgumentException,
                                    IllegalAccessException

      Calls `java.lang.reflect.Field.get(Object)`.

      Parameters:
        `field` - The Field to query.
      Returns:
        The Object from the given Field.
      Throws:
        `IllegalArgumentException` - see `Field.get(Object)`
        `IllegalAccessException` - see `Field.get(Object)`
      See Also:
        `Field.get(Object)`

    - #### isAppendStatics

          public boolean isAppendStatics()

      Gets whether or not to append static fields.

      Returns:
        Whether or not to append static fields.
      Since:
        2.1

    - #### isAppendTransients

          public boolean isAppendTransients()

      Gets whether or not to append transient fields.

      Returns:
        Whether or not to append transient fields.

    - #### reflectionAppendArray

          public ReflectionToStringBuilder reflectionAppendArray(Object array)

      Append to the `toString` an `Object` array.

      Parameters:
        `array` - the array to add to the `toString`
      Returns:
        this

    - #### setAppendStatics

          public void setAppendStatics(boolean appendStatics)

      Sets whether or not to append static fields.

      Parameters:
        `appendStatics` - Whether or not to append static fields.
      Since:
        2.1

    - #### setAppendTransients

          public void setAppendTransients(boolean appendTransients)

      Sets whether or not to append transient fields.

      Parameters:
        `appendTransients` - Whether or not to append transient fields.

    - #### setExcludeFieldNames

          public ReflectionToStringBuilder setExcludeFieldNames(String... excludeFieldNamesParam)

      Sets the field names to exclude.
      Parameters:
        `excludeFieldNamesParam` - The excludeFieldNames to excluding from toString or `null`.
      Returns:
        `this`

    - #### setUpToClass

          public void setUpToClass(Class<?> clazz)

      Sets the last super class to stop appending fields for.

      Parameters:
        `clazz` - The last super class to stop appending fields for.

    - #### toString

          public String toString()

      Gets the String built by this builder.

      Overrides:
        `toString` in class `ToStringBuilder`
      Returns:
        the built string

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