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Apache Commons Lang, a package of Java utility classes for the classes that are in java.lang's hierarchy, or are considered to be so standard as to justify existence in java.lang. The code is tested using the latest revision of the JDK for supported LTS releases: 8, 11, 17 and 21 currently. See https://github.com/apache/commons-lang/blob/master/.github/workflows/maven.yml Please ensure your build environment is up-to-date and kindly report any build issues.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3.builder;

import org.apache.commons.lang3.ObjectUtils;
import org.apache.commons.lang3.Validate;

/**
 * 

Assists in implementing {@link Object#toString()} methods.

* *

This class enables a good and consistent {@code 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: * {@code Person@7f54[name=Stephen,age=29,smoker=false]}

* *

To add the superclass {@code toString}, use {@link #appendSuper}. * To append the {@code toString} from an object that is delegated * to (or any other object), use {@link #appendToString}.

* *

Alternatively, there is a method that uses reflection to determine * the fields to test. Because these fields are usually private, the method, * {@code reflectionToString}, uses {@code 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.

* *

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 {@code toString} is determined by * the {@link ToStringStyle} passed into the constructor.

* * @since 1.0 */ public class ToStringBuilder implements Builder { /** * The default style of output to use, not null. */ private static volatile ToStringStyle defaultStyle = ToStringStyle.DEFAULT_STYLE; //---------------------------------------------------------------------------- /** *

Gets the default {@code 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 {@code ToStringStyle} to the constructor instead * of using this global default.

* *

This method can be used from multiple threads. * Internally, a {@code volatile} variable is used to provide the guarantee * that the latest value set using {@link #setDefaultStyle} 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.

* * @return the default {@code ToStringStyle}, never null */ public static ToStringStyle getDefaultStyle() { return defaultStyle; } /** *

Sets the default {@code 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 {@code ToStringStyle} to the constructor instead * of changing this global default.

* *

This method is not intended for use from multiple threads. * Internally, a {@code volatile} variable is used to provide the guarantee * that the latest value set is the value returned from {@link #getDefaultStyle}.

* * @param style the default {@code ToStringStyle} * @throws IllegalArgumentException if the style is {@code null} */ public static void setDefaultStyle(final ToStringStyle style) { defaultStyle = Validate.notNull(style, "The style must not be null"); } //---------------------------------------------------------------------------- /** *

Uses {@code ReflectionToStringBuilder} to generate a * {@code toString} for the specified object.

* * @param object the Object to be output * @return the String result * @see ReflectionToStringBuilder#toString(Object) */ public static String reflectionToString(final Object object) { return ReflectionToStringBuilder.toString(object); } /** *

Uses {@code ReflectionToStringBuilder} to generate a * {@code toString} for the specified object.

* * @param object the Object to be output * @param style the style of the {@code toString} to create, may be {@code null} * @return the String result * @see ReflectionToStringBuilder#toString(Object,ToStringStyle) */ public static String reflectionToString(final Object object, final ToStringStyle style) { return ReflectionToStringBuilder.toString(object, style); } /** *

Uses {@code ReflectionToStringBuilder} to generate a * {@code toString} for the specified object.

* * @param object the Object to be output * @param style the style of the {@code toString} to create, may be {@code null} * @param outputTransients whether to include transient fields * @return the String result * @see ReflectionToStringBuilder#toString(Object,ToStringStyle,boolean) */ public static String reflectionToString(final Object object, final ToStringStyle style, final boolean outputTransients) { return ReflectionToStringBuilder.toString(object, style, outputTransients, false, null); } /** *

Uses {@code ReflectionToStringBuilder} to generate a * {@code toString} for the specified object.

* * @param the type of the object * @param object the Object to be output * @param style the style of the {@code toString} to create, may be {@code null} * @param outputTransients whether to include transient fields * @param reflectUpToClass the superclass to reflect up to (inclusive), may be {@code null} * @return the String result * @see ReflectionToStringBuilder#toString(Object,ToStringStyle,boolean,boolean,Class) * @since 2.0 */ public static String reflectionToString( final T object, final ToStringStyle style, final boolean outputTransients, final Class reflectUpToClass) { return ReflectionToStringBuilder.toString(object, style, outputTransients, false, reflectUpToClass); } //---------------------------------------------------------------------------- /** * Current toString buffer, not null. */ private final StringBuffer buffer; /** * The object being output, may be null. */ private final Object object; /** * The style of output to use, not null. */ private final ToStringStyle style; /** *

Constructs a builder for the specified object using the default output style.

* *

This default style is obtained from {@link #getDefaultStyle()}.

* * @param object the Object to build a {@code toString} for, not recommended to be null */ public ToStringBuilder(final Object object) { this(object, null, null); } /** *

Constructs a builder for the specified object using the defined output style.

* *

If the style is {@code null}, the default style is used.

* * @param object the Object to build a {@code toString} for, not recommended to be null * @param style the style of the {@code toString} to create, null uses the default style */ public ToStringBuilder(final Object object, final ToStringStyle style) { this(object, style, null); } /** *

Constructs a builder for the specified object.

* *

If the style is {@code null}, the default style is used.

* *

If the buffer is {@code null}, a new one is created.

* * @param object the Object to build a {@code toString} for, not recommended to be null * @param style the style of the {@code toString} to create, null uses the default style * @param buffer the {@code StringBuffer} to populate, may be null */ public ToStringBuilder(final Object object, ToStringStyle style, StringBuffer buffer) { if (style == null) { style = getDefaultStyle(); } if (buffer == null) { buffer = new StringBuffer(512); } this.buffer = buffer; this.style = style; this.object = object; style.appendStart(buffer, object); } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code boolean} * value.

* * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final boolean value) { style.append(buffer, null, value); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code boolean} * array.

* * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final boolean[] array) { style.append(buffer, null, array, null); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code byte} * value.

* * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final byte value) { style.append(buffer, null, value); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code byte} * array.

* * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final byte[] array) { style.append(buffer, null, array, null); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code char} * value.

* * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final char value) { style.append(buffer, null, value); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code char} * array.

* * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final char[] array) { style.append(buffer, null, array, null); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code double} * value.

* * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final double value) { style.append(buffer, null, value); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code double} * array.

* * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final double[] array) { style.append(buffer, null, array, null); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code float} * value.

* * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final float value) { style.append(buffer, null, value); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code float} * array.

* * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final float[] array) { style.append(buffer, null, array, null); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} an {@code int} * value.

* * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final int value) { style.append(buffer, null, value); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} an {@code int} * array.

* * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final int[] array) { style.append(buffer, null, array, null); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code long} * value.

* * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final long value) { style.append(buffer, null, value); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code long} * array.

* * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final long[] array) { style.append(buffer, null, array, null); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} an {@code Object} * value.

* * @param obj the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final Object obj) { style.append(buffer, null, obj, null); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} an {@code Object} * array.

* * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final Object[] array) { style.append(buffer, null, array, null); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code short} * value.

* * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final short value) { style.append(buffer, null, value); return this; } //---------------------------------------------------------------------------- /** *

Append to the {@code toString} a {@code short} * array.

* * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final short[] array) { style.append(buffer, null, array, null); return this; } /** *

Append to the {@code toString} a {@code boolean} * value.

* * @param fieldName the field name * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final boolean value) { style.append(buffer, fieldName, value); return this; } /** *

Append to the {@code toString} a {@code boolean} * array.

* * @param fieldName the field name * @param array the array to add to the {@code hashCode} * @return this */ public ToStringBuilder append(final String fieldName, final boolean[] array) { style.append(buffer, fieldName, array, null); return this; } /** *

Append to the {@code toString} a {@code boolean} * array.

* *

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

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @param fullDetail {@code true} for detail, {@code false} * for summary info * @return this */ public ToStringBuilder append(final String fieldName, final boolean[] array, final boolean fullDetail) { style.append(buffer, fieldName, array, Boolean.valueOf(fullDetail)); return this; } /** *

Append to the {@code toString} an {@code byte} * value.

* * @param fieldName the field name * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final byte value) { style.append(buffer, fieldName, value); return this; } /** *

Append to the {@code toString} a {@code byte} array.

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final byte[] array) { style.append(buffer, fieldName, array, null); return this; } /** *

Append to the {@code toString} a {@code byte} * array.

* *

A boolean parameter controls the level of detail to show. * Setting {@code true} will output the array in full. Setting * {@code false} will output a summary, typically the size of * the array. * * @param fieldName the field name * @param array the array to add to the {@code toString} * @param fullDetail {@code true} for detail, {@code false} * for summary info * @return this */ public ToStringBuilder append(final String fieldName, final byte[] array, final boolean fullDetail) { style.append(buffer, fieldName, array, Boolean.valueOf(fullDetail)); return this; } /** *

Append to the {@code toString} a {@code char} * value.

* * @param fieldName the field name * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final char value) { style.append(buffer, fieldName, value); return this; } /** *

Append to the {@code toString} a {@code char} * array.

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final char[] array) { style.append(buffer, fieldName, array, null); return this; } /** *

Append to the {@code toString} a {@code char} * array.

* *

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

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @param fullDetail {@code true} for detail, {@code false} * for summary info * @return this */ public ToStringBuilder append(final String fieldName, final char[] array, final boolean fullDetail) { style.append(buffer, fieldName, array, Boolean.valueOf(fullDetail)); return this; } /** *

Append to the {@code toString} a {@code double} * value.

* * @param fieldName the field name * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final double value) { style.append(buffer, fieldName, value); return this; } /** *

Append to the {@code toString} a {@code double} * array.

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final double[] array) { style.append(buffer, fieldName, array, null); return this; } /** *

Append to the {@code toString} a {@code double} * array.

* *

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

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @param fullDetail {@code true} for detail, {@code false} * for summary info * @return this */ public ToStringBuilder append(final String fieldName, final double[] array, final boolean fullDetail) { style.append(buffer, fieldName, array, Boolean.valueOf(fullDetail)); return this; } /** *

Append to the {@code toString} an {@code float} * value.

* * @param fieldName the field name * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final float value) { style.append(buffer, fieldName, value); return this; } /** *

Append to the {@code toString} a {@code float} * array.

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final float[] array) { style.append(buffer, fieldName, array, null); return this; } /** *

Append to the {@code toString} a {@code float} * array.

* *

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

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @param fullDetail {@code true} for detail, {@code false} * for summary info * @return this */ public ToStringBuilder append(final String fieldName, final float[] array, final boolean fullDetail) { style.append(buffer, fieldName, array, Boolean.valueOf(fullDetail)); return this; } /** *

Append to the {@code toString} an {@code int} * value.

* * @param fieldName the field name * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final int value) { style.append(buffer, fieldName, value); return this; } /** *

Append to the {@code toString} an {@code int} * array.

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final int[] array) { style.append(buffer, fieldName, array, null); return this; } /** *

Append to the {@code toString} an {@code int} * array.

* *

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

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @param fullDetail {@code true} for detail, {@code false} * for summary info * @return this */ public ToStringBuilder append(final String fieldName, final int[] array, final boolean fullDetail) { style.append(buffer, fieldName, array, Boolean.valueOf(fullDetail)); return this; } /** *

Append to the {@code toString} a {@code long} * value.

* * @param fieldName the field name * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final long value) { style.append(buffer, fieldName, value); return this; } /** *

Append to the {@code toString} a {@code long} * array.

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final long[] array) { style.append(buffer, fieldName, array, null); return this; } /** *

Append to the {@code toString} a {@code long} * array.

* *

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

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @param fullDetail {@code true} for detail, {@code false} * for summary info * @return this */ public ToStringBuilder append(final String fieldName, final long[] array, final boolean fullDetail) { style.append(buffer, fieldName, array, Boolean.valueOf(fullDetail)); return this; } /** *

Append to the {@code toString} an {@code Object} * value.

* * @param fieldName the field name * @param obj the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final Object obj) { style.append(buffer, fieldName, obj, null); return this; } /** *

Append to the {@code toString} an {@code Object} * value.

* * @param fieldName the field name * @param obj the value to add to the {@code toString} * @param fullDetail {@code true} for detail, * {@code false} for summary info * @return this */ public ToStringBuilder append(final String fieldName, final Object obj, final boolean fullDetail) { style.append(buffer, fieldName, obj, Boolean.valueOf(fullDetail)); return this; } /** *

Append to the {@code toString} an {@code Object} * array.

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final Object[] array) { style.append(buffer, fieldName, array, null); return this; } /** *

Append to the {@code toString} an {@code Object} * array.

* *

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

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @param fullDetail {@code true} for detail, {@code false} * for summary info * @return this */ public ToStringBuilder append(final String fieldName, final Object[] array, final boolean fullDetail) { style.append(buffer, fieldName, array, Boolean.valueOf(fullDetail)); return this; } /** *

Append to the {@code toString} an {@code short} * value.

* * @param fieldName the field name * @param value the value to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final short value) { style.append(buffer, fieldName, value); return this; } /** *

Append to the {@code toString} a {@code short} * array.

* * @param fieldName the field name * @param array the array to add to the {@code toString} * @return this */ public ToStringBuilder append(final String fieldName, final short[] array) { style.append(buffer, fieldName, array, null); return this; } /** *

Append to the {@code toString} a {@code short} * array.

* *

A boolean parameter controls the level of detail to show. * Setting {@code true} will output the array in full. Setting * {@code false} will output a summary, typically the size of * the array. * * @param fieldName the field name * @param array the array to add to the {@code toString} * @param fullDetail {@code true} for detail, {@code false} * for summary info * @return this */ public ToStringBuilder append(final String fieldName, final short[] array, final boolean fullDetail) { style.append(buffer, fieldName, array, Boolean.valueOf(fullDetail)); return this; } /** *

Appends with the same format as the default Object toString() * method. Appends the class name followed by * {@link System#identityHashCode(java.lang.Object)}.

* * @param srcObject the {@code Object} whose class name and id to output * @return this * @since 2.0 */ public ToStringBuilder appendAsObjectToString(final Object srcObject) { ObjectUtils.identityToString(this.getStringBuffer(), srcObject); return this; } //---------------------------------------------------------------------------- /** *

Append the {@code toString} from the superclass.

* *

This method assumes that the superclass uses the same {@code ToStringStyle} * as this one.

* *

If {@code superToString} is {@code null}, no change is made.

* * @param superToString the result of {@code super.toString()} * @return this * @since 2.0 */ public ToStringBuilder appendSuper(final String superToString) { if (superToString != null) { style.appendSuper(buffer, superToString); } return this; } /** *

Append the {@code 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 {@code 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 {@code ToStringStyle} * as this one.

* *

If the {@code toString} is {@code null}, no change is made.

* * @param toString the result of {@code toString()} on another object * @return this * @since 2.0 */ public ToStringBuilder appendToString(final String toString) { if (toString != null) { style.appendToString(buffer, toString); } return this; } /** *

Returns the {@code Object} being output.

* * @return The object being output. * @since 2.0 */ public Object getObject() { return object; } /** *

Gets the {@code StringBuffer} being populated.

* * @return the {@code StringBuffer} being populated */ public StringBuffer getStringBuffer() { return buffer; } //---------------------------------------------------------------------------- /** *

Gets the {@code ToStringStyle} being used.

* * @return the {@code ToStringStyle} being used * @since 2.0 */ public ToStringStyle getStyle() { return style; } /** *

Returns the built {@code toString}.

* *

This method appends the end of data indicator, and can only be called once. * Use {@link #getStringBuffer} to get the current string state.

* *

If the object is {@code null}, return the style's {@code nullText}

* * @return the String {@code toString} */ @Override public String toString() { if (this.getObject() == null) { this.getStringBuffer().append(this.getStyle().getNullText()); } else { style.appendEnd(this.getStringBuffer(), this.getObject()); } return this.getStringBuffer().toString(); } /** * Returns the String that was build as an object representation. The * default implementation utilizes the {@link #toString()} implementation. * * @return the String {@code toString} * * @see #toString() * * @since 3.0 */ @Override public String build() { return toString(); } }




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