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Public API for the Apache MyFaces Trinidad project
/*
* 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.myfaces.trinidad.util;
/**
* Helper class to build strings for diagnostic log messages which benefit from detailed information,
* and in toString() implementations.
*
* This class takes care of few niceties like:
* 1. Adding the identity (classname and hashcode) of an object
* 2. Adding fields and values of an object, ensuring null value fields are excluded
* 3. Formatting the string in JSON style
* 4. Adopts a builder pattern, hence easy to use
*
* Note that this class is intended to be used in a single thread and is not thread safe.
*
* Example use:
*
*
* public class CustomClass
* {
* private String fieldOne = "HELLO";
* private Object fieldTwo = null;
* private boolean fieldThree = false;
* private List fieldFour = new ArrayList(Arrays.asList("one","two","three"));
*
* public String toString()
* {
* return
* new ToStringHelper(this).
* append("fieldOne", fieldOne).
* append("fieldTwo", fieldTwo).
* append("fieldThree", fieldThree).
* append("fieldFour", fieldFour).
* toString();
* }
* }
*
*
* Return value of toString() in above example will be
* "CustomClass@19621457 {fieldOne: HELLO, fieldThree: false, fieldFour: [one, two, three]}
"
*/
public final class ToStringHelper
{
public ToStringHelper()
{
this(null);
}
/**
* Constructor that takes in the object whose information is to be added to the string
* @param object The object whose classname and hashcode is to be included in the string
*/
public ToStringHelper(Object object)
{
_builder = new StringBuilder();
if (object != null)
{
_builder.append(object.getClass().getName());
_builder.append("@");
_builder.append(System.identityHashCode(object));
}
}
/**
* Appends the field name and value (as returned by 'toString()' of the supplied value object),
* formatting it in JSON style
* @param fieldName The name of the field to append
* @param value The value object of the field to append
* @return The helper object after appending
*/
public ToStringHelper append(String fieldName, Object value)
{
if (fieldName != null)
{
String stringValue = null;
if (value != null)
{
stringValue = value.toString();
}
_append(fieldName, stringValue);
}
return this;
}
/**
* Appends the field name and value string, formatting it in JSON style
* @param fieldName The name of the field to append
* @param value The value string of the field to append
* @return The helper object after appending
*/
private ToStringHelper _append(String fieldName, String value)
{
if (value == null)
{
if (_STYLE.isNullFieldAppended())
{
value = _STYLE.getNullText();
}
else
{
return this;
}
}
_appendNonNullNameValuePair(fieldName, value);
return this;
}
private void _appendNonNullNameValuePair(String fieldName, String value)
{
if (fieldName != null && value != null)
{
StringBuilder pair = new StringBuilder();
int contentEndIndex = _builder.lastIndexOf(_STYLE.getContentEnd());
// if we have not added the field-value end marker, add it once
if (contentEndIndex == -1)
{
_builder.append(_SPACE);
_builder.append(_STYLE.getContentStart());
_builder.append(_STYLE.getContentEnd());
contentEndIndex = _builder.length() - 1;
}
else
{
// we have the end markers, so we have fields already, so just add field separator
pair.append(_STYLE.getFieldSeparator());
pair.append(_SPACE);
}
// add the field-value pair
pair.append(fieldName);
pair.append(_STYLE.getFieldNameValueSeparator());
pair.append(_SPACE);
pair.append(value);
// insert it just before the end marker
_builder.insert(contentEndIndex, pair); // BREAKPOINT
}
}
@Override
public String toString()
{
return _builder.toString();
}
/**
* Interface defining the formatting style that the ToStringHelper can use
*/
private interface StringStyle
{
// character to append before appending field name-value pairs
public String getContentStart();
// character to append after appending field name-value pairs
public String getContentEnd();
// character to use as the separator between two field name-value pairs
public String getFieldSeparator();
// character to use as separator between the name and value of the field
public String getFieldNameValueSeparator();
// tells if we should append null fields
public boolean isNullFieldAppended();
// tells text to use if the field value is null (i.e. if isNullFieldAppended() returns true)
public String getNullText();
}
/**
* JSON style implementation for default use in ToStringHelper
*/
private static class JSONStringStyle implements StringStyle
{
public String getContentStart()
{
return _CONTENT_START;
}
public String getContentEnd()
{
return _CONTENT_END;
}
public String getFieldSeparator()
{
return _FIELD_SEPARATOR;
}
public String getFieldNameValueSeparator()
{
return _FIELD_NAME_VALUE_SEPARATOR;
}
public boolean isNullFieldAppended()
{
return false;
}
public String getNullText()
{
return _NULL_TEXT;
}
private static String _CONTENT_START = "{";
private static String _CONTENT_END = "}";
private static String _FIELD_SEPARATOR = ",";
private static String _FIELD_NAME_VALUE_SEPARATOR = ":";
private static String _NULL_TEXT = "'null'";
}
private final StringBuilder _builder;
private static final StringStyle _STYLE = new JSONStringStyle();
private static final String _SPACE = " ";
}