org.nakedobjects.applib.util.TitleBuffer Maven / Gradle / Ivy
The newest version!
package org.nakedobjects.applib.util;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
/**
* Title buffer is a utility class to help produce titles for objects without having to add lots of guard
* code. It provides two basic method: one to concatenate a title to the buffer; another to append a title
* with a joiner string, taking care adding in necessary spaces. The benefits of using this class is that null
* references are safely ignored (rather than appearing as 'null'), and joiners (a space by default) are only
* added when needed.
*/
public class TitleBuffer {
private static final String SPACE = " ";
/**
* Determines if the specified object's title (from its toString method) is empty. Will
* return true if either: the specified reference is null; the object's toString method
* returns null; or if the toString returns an empty string.
*/
public static boolean isEmpty(final Object object) {
String title = titleFor(object);
return title == null || title.equals("");
}
/**
* Reflectively run the String title() method if it exists, else fall back to the toString() method.
*/
private static String titleFor(Object object) {
if(object == null) {return null;}
else {
Method method;
try {
method = object.getClass().getMethod("title", new Class[0]);
return (String) method.invoke(object, new Object[0]);
} catch (SecurityException e) {
throw new TitleBufferException(e);
} catch (NoSuchMethodException e) {
return object.toString();
} catch (IllegalArgumentException e) {
throw new TitleBufferException(e);
} catch (IllegalAccessException e) {
throw new TitleBufferException(e);
} catch (InvocationTargetException e) {
throw new TitleBufferException(e);
}
}
}
/**
* Determines if the specified text is empty. Will return true if either: the specified reference is null;
* or if the reference is an empty string.
*/
public static boolean isEmpty(final String text) {
return text == null || text.equals("");
}
private final StringBuffer title;
/**
* Creates a new, empty, title object.
*/
public TitleBuffer() {
title = new StringBuffer();
}
/**
* Creates a new title object, containing the title of the specified object.
*/
public TitleBuffer(final Object object) {
this();
concat(object);
}
/**
* Creates a new title object, containing the title of the specified object.
*/
public TitleBuffer(final Object object, final String defaultTitle) {
this();
if (isEmpty(object)) {
concat(defaultTitle);
} else {
concat(object);
}
}
/**
* Creates a new title object, containing the specified text.
*/
public TitleBuffer(final String text) {
this();
concat(text);
}
/**
*
*/
public TitleBuffer append(final int number) {
append(String.valueOf(number));
return this;
}
/**
* Append the title of the specified object.
*/
public TitleBuffer append(final Object object) {
if (!isEmpty(object)) {
appendWithSpace(object);
}
return this;
}
/**
* Appends the title of the specified object, or the specified text if the objects title is null or empty.
* Prepends a space if there is already some text in this title object.
*
* @param object
* the object whose title is to be appended to this title.
* @param defaultValue
* a textual value to be used if the object's title is null or empty.
* @return a reference to the called object (itself).
*/
public TitleBuffer append(final Object object, final String defaultValue) {
if (!isEmpty(object)) {
appendWithSpace(object);
} else {
appendWithSpace(defaultValue);
}
return this;
}
/**
* Appends a space (if there is already some text in this title object) and then the specified text.
*
* @return a reference to the called object (itself).
*/
public TitleBuffer append(final String text) {
if (!isEmpty(text)) {
appendWithSpace(text);
}
return this;
}
/**
* Appends the joining string and the title of the specified object (from its toString
* method). If the object is empty then nothing will be appended.
*
* @see #isEmpty(Object)
*/
public TitleBuffer append(final String joiner, final Object object) {
if (!isEmpty(object)) {
appendJoiner(joiner);
appendWithSpace(object);
}
return this;
}
/**
* Append the joiner text, a space, and the title of the specified naked object (object)
* (got by calling the objects title() method) to the text of this TitleString object. If the title of the
* specified object is null then use the defaultValue text. If both the objects title and
* the default value are null or equate to a zero-length string then no text will be appended ; not even
* the joiner text.
*
* @param joiner
* text to append before the title
* @param object
* object whose title needs to be appended
* @param defaultTitle
* the text to use if the the object's title is null.
* @return a reference to the called object (itself).
*/
public TitleBuffer append(final String joiner, final Object object, final String defaultTitle) {
appendJoiner(joiner);
if (!isEmpty(object)) {
appendWithSpace(object);
} else {
appendWithSpace(defaultTitle);
}
return this;
}
/**
* Appends the joiner text, a space, and the text to the text of this TitleString object. If no text yet
* exists in the object then the joiner text and space are omitted.
*
* @return a reference to the called object (itself).
*/
public TitleBuffer append(final String joiner, final String text) {
if (!isEmpty(text)) {
appendJoiner(joiner);
appendWithSpace(text);
}
return this;
}
private void appendJoiner(final String joiner) {
if (title.length() > 0) {
title.append(joiner);
}
}
/**
* Append a space to the text of this TitleString object if, and only if, there is some existing text
* i.e., a space is only added to existing text and will not create a text entry consisting of only one
* space.
*
* @return a reference to the called object (itself).
*/
public TitleBuffer appendSpace() {
if (title.length() > 0) {
title.append(SPACE);
}
return this;
}
private void appendWithSpace(final Object object) {
appendSpace();
title.append(titleFor(object));
}
/**
* Concatenate the the title value (the result of calling an objects label() method) to this TitleString
* object. If the value is null the no text is added.
*
* @param object
* the naked object to get a title from
* @return a reference to the called object (itself).
*/
public final TitleBuffer concat(final Object object) {
concat(object, "");
return this;
}
/**
* Concatenate the the title value (the result of calling an objects label() method), or the specified
* default value if the title is equal to null or is empty, to this TitleString object.
*
* @param object
* the naked object to get a title from
* @param defaultValue
* the default text to use when the naked object is null
* @return a reference to the called object (itself).
*/
public final TitleBuffer concat(final Object object, final String defaultValue) {
if (isEmpty(object)) {
title.append(defaultValue);
} else {
title.append(titleFor(object));
}
return this;
}
/**
* Concatenate the specified text on to the end of the text of this TitleString.
*
* @param text
* text to append
* @return a reference to the called object (itself).
*/
public final TitleBuffer concat(final String text) {
title.append(text);
return this;
}
public final TitleBuffer concat(final String joiner, final Object object) {
if (!isEmpty(object)) {
appendJoiner(joiner);
concat(object, "");
}
return this;
}
public final TitleBuffer concat(final String joiner, final Object object, final String defaultValue) {
if (isEmpty(object)) {
appendJoiner(joiner);
title.append(defaultValue);
} else {
appendJoiner(joiner);
title.append(titleFor(object));
}
return this;
}
/**
* Returns a String that represents the value of this object.
*/
@Override
public String toString() {
return title.toString();
}
/**
* Truncates this title so it has a maximum number of words. Spaces are used to determine words, thus two
* spaces in a title will cause two words to be mistakenly identified.
*
* @param noWords
* the number of words to show
* @return a reference to the called object (itself).
*/
public TitleBuffer truncate(final int noWords) {
if (noWords < 1) {
throw new IllegalArgumentException("Truncation must be to one or more words");
}
int pos = 0;
int spaces = 0;
while (pos < title.length() && spaces < noWords) {
if (title.charAt(pos) == ' ') {
spaces++;
}
pos++;
}
if (pos < title.length()) {
title.setLength(pos - 1); // string.delete(pos - 1, string.length());
title.append("...");
}
return this;
}
}
// Copyright (c) Naked Objects Group Ltd.