2323
2424/**
2525 * A simple log message type for use with Commons Logging, allowing
26- * for convenient late resolution of a given {@link Supplier} instance
27- * (typically bound to a Java 8 lambda expression) in {@link #toString()}.
26+ * for convenient lazy resolution of a given {@link Supplier} instance
27+ * (typically bound to a Java 8 lambda expression) or a printf-style
28+ * format string ({@link String#format})in its {@link #toString()}.
2829 *
2930 * @author Juergen Hoeller
3031 * @since 5.2
32+ * @see #lazy(Supplier)
33+ * @see #format(String, Object)
34+ * @see #format(String, Object...)
3135 * @see org.apache.commons.logging.Log#fatal(Object)
3236 * @see org.apache.commons.logging.Log#error(Object)
3337 * @see org.apache.commons.logging.Log#warn(Object)
3438 * @see org.apache.commons.logging.Log#info(Object)
3539 * @see org.apache.commons.logging.Log#debug(Object)
3640 * @see org.apache.commons.logging.Log#trace(Object)
3741 */
38- public class LogMessage {
39-
40- private final Supplier <? extends CharSequence > supplier ;
42+ public abstract class LogMessage implements CharSequence {
4143
4244 @ Nullable
4345 private String result ;
4446
4547
46- /**
47- * Construct a new {@code LogMessage} for the given supplier.
48- * @param supplier the lazily resolving supplier
49- * (typically bound to a Java 8 lambda expression)
50- */
51- public LogMessage ( Supplier <? extends CharSequence > supplier ) {
52- Assert . notNull ( supplier , "Supplier must not be null" );
53- this . supplier = supplier ;
48+ @ Override
49+ public int length () {
50+ return toString (). length ();
51+ }
52+
53+ @ Override
54+ public char charAt ( int index ) {
55+ return toString (). charAt ( index ) ;
5456 }
5557
58+ @ Override
59+ public CharSequence subSequence (int start , int end ) {
60+ return toString ().subSequence (start , end );
61+ }
5662
5763 /**
5864 * This will be called by the logging provider, potentially once
@@ -61,9 +67,202 @@ public LogMessage(Supplier<? extends CharSequence> supplier) {
6167 @ Override
6268 public String toString () {
6369 if (this .result == null ) {
64- this .result = this . supplier . get (). toString ();
70+ this .result = buildString ();
6571 }
6672 return this .result ;
6773 }
6874
75+ abstract String buildString ();
76+
77+
78+ /**
79+ * Build a lazy resolution message from the given supplier.
80+ * @param supplier the supplier (typically bound to a Java 8 lambda expression)
81+ * @see #toString()
82+ */
83+ public static LogMessage lazy (Supplier <? extends CharSequence > supplier ) {
84+ return new LazyMessage (supplier );
85+ }
86+
87+ /**
88+ * Build a formatted message from the given format string and argument.
89+ * @param format the format string (following {@link String#format} rules)
90+ * @param arg1 the argument
91+ * @see String#format(String, Object...)
92+ */
93+ public static LogMessage format (String format , Object arg1 ) {
94+ return new FormatMessage1 (format , arg1 );
95+ }
96+
97+ /**
98+ * Build a formatted message from the given format string and arguments.
99+ * @param format the format string (following {@link String#format} rules)
100+ * @param arg1 the first argument
101+ * @param arg2 the second argument
102+ * @see String#format(String, Object...)
103+ */
104+ public static LogMessage format (String format , Object arg1 , Object arg2 ) {
105+ return new FormatMessage2 (format , arg1 , arg2 );
106+ }
107+
108+ /**
109+ * Build a formatted message from the given format string and arguments.
110+ * @param format the format string (following {@link String#format} rules)
111+ * @param arg1 the first argument
112+ * @param arg2 the second argument
113+ * @param arg3 the third argument
114+ * @see String#format(String, Object...)
115+ */
116+ public static LogMessage format (String format , Object arg1 , Object arg2 , Object arg3 ) {
117+ return new FormatMessage3 (format , arg1 , arg2 , arg3 );
118+ }
119+
120+ /**
121+ * Build a formatted message from the given format string and arguments.
122+ * @param format the format string (following {@link String#format} rules)
123+ * @param arg1 the first argument
124+ * @param arg2 the second argument
125+ * @param arg3 the third argument
126+ * @param arg4 the fourth argument
127+ * @see String#format(String, Object...)
128+ */
129+ public static LogMessage format (String format , Object arg1 , Object arg2 , Object arg3 , Object arg4 ) {
130+ return new FormatMessage4 (format , arg1 , arg2 , arg3 , arg4 );
131+ }
132+
133+ /**
134+ * Build a formatted message from the given format string and varargs.
135+ * @param format the format string (following {@link String#format} rules)
136+ * @param args the varargs array (costly, prefer individual arguments)
137+ * @see String#format(String, Object...)
138+ */
139+ public static LogMessage format (String format , Object ... args ) {
140+ return new FormatMessageX (format , args );
141+ }
142+
143+
144+ private static final class LazyMessage extends LogMessage {
145+
146+ private Supplier <? extends CharSequence > supplier ;
147+
148+ LazyMessage (Supplier <? extends CharSequence > supplier ) {
149+ Assert .notNull (supplier , "Supplier must not be null" );
150+ this .supplier = supplier ;
151+ }
152+
153+ @ Override
154+ String buildString () {
155+ return this .supplier .get ().toString ();
156+ }
157+ }
158+
159+
160+ private static abstract class FormatMessage extends LogMessage {
161+
162+ protected final String format ;
163+
164+ FormatMessage (String format ) {
165+ Assert .notNull (format , "Format must not be null" );
166+ this .format = format ;
167+ }
168+ }
169+
170+
171+ private static final class FormatMessage1 extends FormatMessage {
172+
173+ private final Object arg1 ;
174+
175+ FormatMessage1 (String format , Object arg1 ) {
176+ super (format );
177+ this .arg1 = arg1 ;
178+ }
179+
180+ @ Override
181+ protected String buildString () {
182+ return String .format (this .format , this .arg1 );
183+ }
184+ }
185+
186+
187+ private static final class FormatMessage2 extends FormatMessage {
188+
189+ private final Object arg1 ;
190+
191+ private final Object arg2 ;
192+
193+ FormatMessage2 (String format , Object arg1 , Object arg2 ) {
194+ super (format );
195+ this .arg1 = arg1 ;
196+ this .arg2 = arg2 ;
197+ }
198+
199+ @ Override
200+ String buildString () {
201+ return String .format (this .format , this .arg1 , this .arg2 );
202+ }
203+ }
204+
205+
206+ private static final class FormatMessage3 extends FormatMessage {
207+
208+ private final Object arg1 ;
209+
210+ private final Object arg2 ;
211+
212+ private final Object arg3 ;
213+
214+ FormatMessage3 (String format , Object arg1 , Object arg2 , Object arg3 ) {
215+ super (format );
216+ this .arg1 = arg1 ;
217+ this .arg2 = arg2 ;
218+ this .arg3 = arg3 ;
219+ }
220+
221+ @ Override
222+ String buildString () {
223+ return String .format (this .format , this .arg1 , this .arg2 , this .arg3 );
224+ }
225+ }
226+
227+
228+ private static final class FormatMessage4 extends FormatMessage {
229+
230+ private final Object arg1 ;
231+
232+ private final Object arg2 ;
233+
234+ private final Object arg3 ;
235+
236+ private final Object arg4 ;
237+
238+ FormatMessage4 (String format , Object arg1 , Object arg2 , Object arg3 , Object arg4 ) {
239+ super (format );
240+ this .arg1 = arg1 ;
241+ this .arg2 = arg2 ;
242+ this .arg3 = arg3 ;
243+ this .arg4 = arg4 ;
244+ }
245+
246+ @ Override
247+ String buildString () {
248+ return String .format (this .format , this .arg1 , this .arg2 , this .arg3 , this .arg4 );
249+ }
250+ }
251+
252+
253+ private static final class FormatMessageX extends FormatMessage {
254+
255+ private final Object [] args ;
256+
257+ FormatMessageX (String format , Object ... args ) {
258+ super (format );
259+ this .args = args ;
260+ }
261+
262+ @ Override
263+ String buildString () {
264+ return String .format (this .format , this .args );
265+ }
266+ }
267+
69268}
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