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/*
* Copyright 2002-2019 the original author or authors.
*
* Licensed 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
*
* https://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.springframework.core.log;
import java.util.function.Supplier;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
/**
* A simple log message type for use with Commons Logging, allowing
* for convenient lazy resolution of a given {@link Supplier} instance
* (typically bound to a Java 8 lambda expression) or a printf-style
* format string ({@link String#format}) in its {@link #toString()}.
*
* @author Juergen Hoeller
* @since 5.2
* @see #of(Supplier)
* @see #format(String, Object)
* @see #format(String, Object...)
* @see org.apache.commons.logging.Log#fatal(Object)
* @see org.apache.commons.logging.Log#error(Object)
* @see org.apache.commons.logging.Log#warn(Object)
* @see org.apache.commons.logging.Log#info(Object)
* @see org.apache.commons.logging.Log#debug(Object)
* @see org.apache.commons.logging.Log#trace(Object)
*/
public abstract class LogMessage implements CharSequence {
@Nullable
private String result;
@Override
public int length() {
return toString().length();
}
@Override
public char charAt(int index) {
return toString().charAt(index);
}
@Override
public CharSequence subSequence(int start, int end) {
return toString().subSequence(start, end);
}
/**
* This will be called by the logging provider, potentially once
* per log target (therefore locally caching the result here).
*/
@Override
public String toString() {
if (this.result == null) {
this.result = buildString();
}
return this.result;
}
abstract String buildString();
/**
* Build a lazily resolving message from the given supplier.
* @param supplier the supplier (typically bound to a Java 8 lambda expression)
* @see #toString()
*/
public static LogMessage of(Supplier supplier) {
return new SupplierMessage(supplier);
}
/**
* Build a lazily formatted message from the given format string and argument.
* @param format the format string (following {@link String#format} rules)
* @param arg1 the argument
* @see String#format(String, Object...)
*/
public static LogMessage format(String format, Object arg1) {
return new FormatMessage1(format, arg1);
}
/**
* Build a lazily formatted message from the given format string and arguments.
* @param format the format string (following {@link String#format} rules)
* @param arg1 the first argument
* @param arg2 the second argument
* @see String#format(String, Object...)
*/
public static LogMessage format(String format, Object arg1, Object arg2) {
return new FormatMessage2(format, arg1, arg2);
}
/**
* Build a lazily formatted message from the given format string and arguments.
* @param format the format string (following {@link String#format} rules)
* @param arg1 the first argument
* @param arg2 the second argument
* @param arg3 the third argument
* @see String#format(String, Object...)
*/
public static LogMessage format(String format, Object arg1, Object arg2, Object arg3) {
return new FormatMessage3(format, arg1, arg2, arg3);
}
/**
* Build a lazily formatted message from the given format string and arguments.
* @param format the format string (following {@link String#format} rules)
* @param arg1 the first argument
* @param arg2 the second argument
* @param arg3 the third argument
* @param arg4 the fourth argument
* @see String#format(String, Object...)
*/
public static LogMessage format(String format, Object arg1, Object arg2, Object arg3, Object arg4) {
return new FormatMessage4(format, arg1, arg2, arg3, arg4);
}
/**
* Build a lazily formatted message from the given format string and varargs.
* @param format the format string (following {@link String#format} rules)
* @param args the varargs array (costly, prefer individual arguments)
* @see String#format(String, Object...)
*/
public static LogMessage format(String format, Object... args) {
return new FormatMessageX(format, args);
}
private static final class SupplierMessage extends LogMessage {
private Supplier supplier;
SupplierMessage(Supplier supplier) {
Assert.notNull(supplier, "Supplier must not be null");
this.supplier = supplier;
}
@Override
String buildString() {
return this.supplier.get().toString();
}
}
private static abstract class FormatMessage extends LogMessage {
protected final String format;
FormatMessage(String format) {
Assert.notNull(format, "Format must not be null");
this.format = format;
}
}
private static final class FormatMessage1 extends FormatMessage {
private final Object arg1;
FormatMessage1(String format, Object arg1) {
super(format);
this.arg1 = arg1;
}
@Override
protected String buildString() {
return String.format(this.format, this.arg1);
}
}
private static final class FormatMessage2 extends FormatMessage {
private final Object arg1;
private final Object arg2;
FormatMessage2(String format, Object arg1, Object arg2) {
super(format);
this.arg1 = arg1;
this.arg2 = arg2;
}
@Override
String buildString() {
return String.format(this.format, this.arg1, this.arg2);
}
}
private static final class FormatMessage3 extends FormatMessage {
private final Object arg1;
private final Object arg2;
private final Object arg3;
FormatMessage3(String format, Object arg1, Object arg2, Object arg3) {
super(format);
this.arg1 = arg1;
this.arg2 = arg2;
this.arg3 = arg3;
}
@Override
String buildString() {
return String.format(this.format, this.arg1, this.arg2, this.arg3);
}
}
private static final class FormatMessage4 extends FormatMessage {
private final Object arg1;
private final Object arg2;
private final Object arg3;
private final Object arg4;
FormatMessage4(String format, Object arg1, Object arg2, Object arg3, Object arg4) {
super(format);
this.arg1 = arg1;
this.arg2 = arg2;
this.arg3 = arg3;
this.arg4 = arg4;
}
@Override
String buildString() {
return String.format(this.format, this.arg1, this.arg2, this.arg3, this.arg4);
}
}
private static final class FormatMessageX extends FormatMessage {
private final Object[] args;
FormatMessageX(String format, Object... args) {
super(format);
this.args = args;
}
@Override
String buildString() {
return String.format(this.format, this.args);
}
}
}
