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();
 }
 

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

Method Summary

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.
boolean	isExcludeNullValues() Gets whether or not to append fields whose values are null.
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	setExcludeNullValues(boolean excludeNullValues) Sets whether or not to append fields whose values are null.
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, boolean excludeNullValues, Class<? super T> reflectUpToClass) 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

ReflectionToStringBuilder

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

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

excludeNullValues - whether to exclude fields who value is null

Since:

3.6

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

See Also:

ToStringExclude, ToStringSummary

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:

ToStringExclude, ToStringSummary

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:

ToStringExclude, ToStringSummary

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:

ToStringExclude, ToStringSummary

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

See Also:

ToStringExclude, ToStringSummary

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 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

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:

ToStringExclude, ToStringSummary

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 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.

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)

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.

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

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