Package 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:

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();
 }

Alternatively the ToStringExclude annotation can be used to exclude fields from being incorporated in the result.

It is also possible to use the ToStringSummary annotation to output the summary information instead of the detailed information of a field.

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

  • Field Details

    • 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

    • includeFieldNames

      protected String[] includeFieldNames
      Field names that will be included in the output. All fields are included by default.
      Since:
      3.13.0

  • Constructor Details

    • ReflectionToStringBuilder

      public ReflectionToStringBuilder(Object object)
      Constructs a new instance.

      This constructor outputs using the default style set with setDefaultStyle.

      Parameters:
      object - the Object to build a toString for, must not be null

    • ReflectionToStringBuilder

      public ReflectionToStringBuilder(Object object, ToStringStyle style)
      Constructs a new instance.

      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

    • ReflectionToStringBuilder

      public ReflectionToStringBuilder(Object object, ToStringStyle style, StringBuffer buffer)
      Constructs a new instance.

      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

    • ReflectionToStringBuilder

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

    • ReflectionToStringBuilder

      public ReflectionToStringBuilder(T object, ToStringStyle style, StringBuffer buffer, Class<? super T> reflectUpToClass, boolean outputTransients, boolean outputStatics, boolean excludeNullValues)
      Constructs a new instance.
      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
      excludeNullValues - whether to exclude fields who value is null
      Since:
      3.6

  • Method Details

    • 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
      See Also:

    • 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
      See Also:

    • 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
      See Also:

    • 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 static fields
      Returns:
      the String result
      Throws:
      IllegalArgumentException - if the Object is null
      Since:
      2.1
      See Also:

    • toString

      public static <T> String toString(T object, ToStringStyle style, boolean outputTransients, boolean outputStatics, boolean excludeNullValues, 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 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
      excludeNullValues - whether to exclude fields whose values are null
      reflectUpToClass - the superclass to reflect up to (inclusive), may be null
      Returns:
      the String result
      Throws:
      IllegalArgumentException - if the Object is null
      Since:
      3.6
      See Also:

    • 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 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
      See Also:

    • 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.

    • toStringInclude

      public static String toStringInclude(Object object, Collection<String> includeFieldNames)
      Builds a String for a toString method including the given field names.
      Parameters:
      object - The object to "toString".
      includeFieldNames - null or empty means all fields are included. All fields are included by default. This method will override the default behavior.
      Returns:
      The toString value.
      Since:
      3.13.0

    • toStringInclude

      public static String toStringInclude(Object object, String... includeFieldNames)
      Builds a String for a toString method including the given field names.
      Parameters:
      object - The object to "toString".
      includeFieldNames - The field names to include. null or empty means all fields are included. All fields are included by default. This method will override the default behavior.
      Returns:
      The toString value.
      Since:
      3.13.0

    • accept

      protected boolean accept(Field field)
      Returns whether or not to append the given Field.
      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()
      Gets the excludeFieldNames.
      Returns:
      the excludeFieldNames.

    • getIncludeFieldNames

      public String[] getIncludeFieldNames()
      Gets the includeFieldNames
      Returns:
      the includeFieldNames.
      Since:
      3.13.0

    • 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 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:

    • 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.

    • isExcludeNullValues

      public boolean isExcludeNullValues()
      Gets whether or not to append fields whose values are null.
      Returns:
      Whether or not to append fields whose values are null.
      Since:
      3.6

    • reflectionAppendArray

      public ReflectionToStringBuilder reflectionAppendArray(Object array)
      Appends to the toString an Object array.
      Parameters:
      array - the array to add to the toString
      Returns:
      this instance.

    • 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

    • setExcludeNullValues

      public void setExcludeNullValues(boolean excludeNullValues)
      Sets whether or not to append fields whose values are null.
      Parameters:
      excludeNullValues - Whether or not to append fields whose values are null.
      Since:
      3.6

    • setIncludeFieldNames

      public ReflectionToStringBuilder setIncludeFieldNames(String... includeFieldNamesParam)
      Sets the field names to include. null or empty means all fields are included. All fields are included by default. This method will override the default behavior.
      Parameters:
      includeFieldNamesParam - The includeFieldNames that must be on toString or null.
      Returns:
      this
      Since:
      3.13.0

    • 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