Class ToStringBuilder

java.lang.Object
org.apache.commons.lang3.builder.AbstractReflection
org.apache.commons.lang3.builder.ToStringBuilder
All Implemented Interfaces:
Builder<String>
Direct Known Subclasses:
ReflectionToStringBuilder
public class ToStringBuilder extends AbstractReflection implements Builder<String>
Assists in implementing Object.toString() methods.

This class enables a good and consistent toString() to be built for any class or object. This class aims to simplify the process by:

  • allowing field names
  • handling all types consistently
  • handling nulls consistently
  • outputting arrays and multi-dimensional arrays
  • enabling the detail level to be controlled for Objects and Collections
  • handling class hierarchies

To use this class write code as follows: 

public class Person {
  String name;
  int age;
  boolean smoker;

  ...

  public String toString() {
    return new ToStringBuilder(this).
      append("name", name).
      append("age", age).
      append("smoker", smoker).
      toString();
  }
}

This will produce a toString of the format: Person@7f54[name=Stephen,age=29,smoker=false]

To add the superclass toString, use appendSuper(String). To append the toString from an object that is delegated to (or any other object), use appendToString(String).

Alternatively, there is a method that uses reflection to determine the fields to test. Because these fields are usually private, the method, reflectionToString, uses AccessibleObject.setAccessible to change the visibility of the fields. This will fail under a security manager, unless the appropriate permissions are set up correctly. It is also slower than testing explicitly.

See also AbstractReflection.AbstractBuilder.setForceAccessible(boolean)

A typical invocation for this method would look like: 

public String toString() {
  return ToStringBuilder.reflectionToString(this);
}

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

System.out.println("An object: " + ToStringBuilder.reflectionToString(anObject));

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

Since:
1.0
See Also:

  • Constructor Details

    • ToStringBuilder

      public ToStringBuilder(Object object)
      Constructs a builder for the specified object using the default output style.

      This default style is obtained from getDefaultStyle().

      Parameters:
      object - The Object to build a toString for, not recommended to be null

    • ToStringBuilder

      public ToStringBuilder(Object object, ToStringStyle style)
      Constructs a builder for the specified object using the defined output style.

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

      Parameters:
      object - The Object to build a toString for, not recommended to be null
      style - The style of the toString to create, null uses the default style

    • ToStringBuilder

      public ToStringBuilder(Object object, ToStringStyle style, StringBuffer buffer)
      Constructs a builder for the specified object.

      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, not recommended to be null
      style - The style of the toString to create, null uses the default style
      buffer - The StringBuffer to populate, may be null

  • Method Details

    • builder

      public static ToStringBuilder.Builder builder()
      Constructs a new Builder.
      Returns:
      A new Builder.
      Since:
      3.21.0

    • getDefaultStyle

      public static ToStringStyle getDefaultStyle()
      Gets the default ToStringStyle to use.

      This method gets a singleton default value, typically for the whole JVM. Changing this default should generally only be done during application startup. It is recommended to pass a ToStringStyle to the constructor instead of using this global default.

      This method can be used from multiple threads. Internally, a volatile variable is used to provide the guarantee that the latest value set using setDefaultStyle(ToStringStyle) is the value returned. It is strongly recommended that the default style is only changed during application startup.

      One reason for changing the default could be to have a verbose style during development and a compact style in production.

      Returns:
      The default ToStringStyle, never null

    • reflectionToString

      public static String reflectionToString(Object object)
      Uses ReflectionToStringBuilder to generate a toString for the specified object.
      Parameters:
      object - The Object to be output
      Returns:
      The String result
      See Also:

    • reflectionToString

      public static String reflectionToString(Object object, ToStringStyle style)
      Uses ReflectionToStringBuilder to generate a toString for the specified object.
      Parameters:
      object - The Object to be output
      style - The style of the toString to create, may be null
      Returns:
      The String result
      See Also:

    • reflectionToString

      public static String reflectionToString(Object object, ToStringStyle style, boolean outputTransients)
      Uses ReflectionToStringBuilder to generate a toString for the specified 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
      Returns:
      The String result
      See Also:

    • reflectionToString

      public static <T> String reflectionToString(T object, ToStringStyle style, boolean outputTransients, Class<? super T> reflectUpToClass)
      Uses ReflectionToStringBuilder to generate a toString for the specified object.
      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
      reflectUpToClass - The superclass to reflect up to (inclusive), may be null
      Returns:
      The String result
      Since:
      2.0
      See Also:

    • setDefaultStyle

      public static void setDefaultStyle(ToStringStyle style)
      Sets the default ToStringStyle to use.

      This method sets a singleton default value, typically for the whole JVM. Changing this default should generally only be done during application startup. It is recommended to pass a ToStringStyle to the constructor instead of changing this global default.

      This method is not intended for use from multiple threads. Internally, a volatile variable is used to provide the guarantee that the latest value set is the value returned from getDefaultStyle().

      Parameters:
      style - The default ToStringStyle
      Throws:
      NullPointerException - Thrown if the style is null.

    • append

      public ToStringBuilder append(boolean value)
      Appends to the toString a boolean value.
      Parameters:
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(boolean[] array)
      Appends to the toString a boolean array.
      Parameters:
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(byte value)
      Appends to the toString a byte value.
      Parameters:
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(byte[] array)
      Appends to the toString a byte array.
      Parameters:
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(char value)
      Appends to the toString a char value.
      Parameters:
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(char[] array)
      Appends to the toString a char array.
      Parameters:
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(double value)
      Appends to the toString a double value.
      Parameters:
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(double[] array)
      Appends to the toString a double array.
      Parameters:
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(float value)
      Appends to the toString a float value.
      Parameters:
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(float[] array)
      Appends to the toString a float array.
      Parameters:
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(int value)
      Appends to the toString an int value.
      Parameters:
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(int[] array)
      Appends to the toString an int array.
      Parameters:
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(long value)
      Appends to the toString a long value.
      Parameters:
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(long[] array)
      Appends to the toString a long array.
      Parameters:
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(Object obj)
      Appends to the toString an Object value.
      Parameters:
      obj - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(Object[] array)
      Appends to the toString an Object array.
      Parameters:
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(short value)
      Appends to the toString a short value.
      Parameters:
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(short[] array)
      Appends to the toString a short array.
      Parameters:
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, boolean value)
      Appends to the toString a boolean value.
      Parameters:
      fieldName - The field name
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, boolean[] array)
      Appends to the toString a boolean array.
      Parameters:
      fieldName - The field name
      array - The array to add to the hashCode
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, boolean[] array, boolean fullDetail)
      Appends to the toString a boolean array.

      A boolean parameter controls the level of detail to show. Setting true will output the array in full. Setting false will output a summary, typically the size of the array.

      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      fullDetail - true for detail, false for summary info
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, byte value)
      Appends to the toString an byte value.
      Parameters:
      fieldName - The field name
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, byte[] array)
      Appends to the toString a byte array.
      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, byte[] array, boolean fullDetail)
      Appends to the toString a byte array.

      A boolean parameter controls the level of detail to show. Setting true will output the array in full. Setting false will output a summary, typically the size of the array.

      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      fullDetail - true for detail, false for summary info
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, char value)
      Appends to the toString a char value.
      Parameters:
      fieldName - The field name
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, char[] array)
      Appends to the toString a char array.
      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, char[] array, boolean fullDetail)
      Appends to the toString a char array.

      A boolean parameter controls the level of detail to show. Setting true will output the array in full. Setting false will output a summary, typically the size of the array.

      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      fullDetail - true for detail, false for summary info
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, double value)
      Appends to the toString a double value.
      Parameters:
      fieldName - The field name
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, double[] array)
      Appends to the toString a double array.
      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, double[] array, boolean fullDetail)
      Appends to the toString a double array.

      A boolean parameter controls the level of detail to show. Setting true will output the array in full. Setting false will output a summary, typically the size of the array.

      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      fullDetail - true for detail, false for summary info
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, float value)
      Appends to the toString an float value.
      Parameters:
      fieldName - The field name
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, float[] array)
      Appends to the toString a float array.
      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, float[] array, boolean fullDetail)
      Appends to the toString a float array.

      A boolean parameter controls the level of detail to show. Setting true will output the array in full. Setting false will output a summary, typically the size of the array.

      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      fullDetail - true for detail, false for summary info
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, int value)
      Appends to the toString an int value.
      Parameters:
      fieldName - The field name
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, int[] array)
      Appends to the toString an int array.
      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, int[] array, boolean fullDetail)
      Appends to the toString an int array.

      A boolean parameter controls the level of detail to show. Setting true will output the array in full. Setting false will output a summary, typically the size of the array.

      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      fullDetail - true for detail, false for summary info
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, long value)
      Appends to the toString a long value.
      Parameters:
      fieldName - The field name
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, long[] array)
      Appends to the toString a long array.
      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, long[] array, boolean fullDetail)
      Appends to the toString a long array.

      A boolean parameter controls the level of detail to show. Setting true will output the array in full. Setting false will output a summary, typically the size of the array.

      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      fullDetail - true for detail, false for summary info
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, Object obj)
      Appends to the toString an Object value.
      Parameters:
      fieldName - The field name
      obj - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, Object obj, boolean fullDetail)
      Appends to the toString an Object value.
      Parameters:
      fieldName - The field name
      obj - The value to add to the toString
      fullDetail - true for detail, false for summary info
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, Object[] array)
      Appends to the toString an Object array.
      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, Object[] array, boolean fullDetail)
      Appends to the toString an Object array.

      A boolean parameter controls the level of detail to show. Setting true will output the array in full. Setting false will output a summary, typically the size of the array.

      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      fullDetail - true for detail, false for summary info
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, short value)
      Appends to the toString an short value.
      Parameters:
      fieldName - The field name
      value - The value to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, short[] array)
      Appends to the toString a short array.
      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      Returns:
      this instance.

    • append

      public ToStringBuilder append(String fieldName, short[] array, boolean fullDetail)
      Appends to the toString a short array.

      A boolean parameter controls the level of detail to show. Setting true will output the array in full. Setting false will output a summary, typically the size of the array.

      Parameters:
      fieldName - The field name
      array - The array to add to the toString
      fullDetail - true for detail, false for summary info
      Returns:
      this instance.

    • appendAsObjectToString

      public ToStringBuilder appendAsObjectToString(Object srcObject)
      Appends with the same format as the default Object toString() method. Appends the class name followed by System.identityHashCode(Object).
      Parameters:
      srcObject - The Object whose class name and id to output
      Returns:
      this instance.
      Throws:
      NullPointerException - Thrown if srcObject is null.
      Since:
      2.0

    • appendSuper

      public ToStringBuilder appendSuper(String superToString)
      Append the toString from the superclass.

      This method assumes that the superclass uses the same ToStringStyle as this one.

      If superToString is null, no change is made.

      Parameters:
      superToString - The result of super.toString()
      Returns:
      this instance.
      Since:
      2.0

    • appendToString

      public ToStringBuilder appendToString(String toString)
      Append the toString from another object.

      This method is useful where a class delegates most of the implementation of its properties to another class. You can then call toString() on the other class and pass the result into this method. 

        private AnotherObject delegate;
  private String fieldInThisClass;

  public String toString() {
    return new ToStringBuilder(this).
      appendToString(delegate.toString()).
      append(fieldInThisClass).
      toString();
  }

      This method assumes that the other object uses the same ToStringStyle as this one.

      If the toString is null, no change is made.

      Parameters:
      toString - The result of toString() on another object
      Returns:
      this instance.
      Since:
      2.0

    • build

      public String build()
      Returns the String that was build as an object representation. The default implementation utilizes the toString() implementation.
      Specified by:
      build in interface Builder<String>
      Returns:
      The String toString
      Since:
      3.0
      See Also:

    • getObject

      public Object getObject()
      Gets the Object being output.
      Returns:
      The object being output.
      Since:
      2.0

    • getStringBuffer

      public StringBuffer getStringBuffer()
      Gets the StringBuffer being populated.
      Returns:
      The StringBuffer being populated

    • getStyle

      public ToStringStyle getStyle()
      Gets the ToStringStyle being used.
      Returns:
      The ToStringStyle being used
      Since:
      2.0

    • toString

      public String toString()
      Returns the built toString.

      This method appends the end of data indicator, and can only be called once. Use getStringBuffer() to get the current string state.

      If the object is null, return the style's nullText

      Overrides:
      toString in class Object
      Returns:
      The String toString