Eclair

Eclair - Java Spring library for AOP logging.

Provides annotations for declarative logging of annotated method execution. Includes abstractions for annotations processing, simple implementation and Spring Boot starter with auto-configuration.

• events logging detected by Spring AOP: beginning, ending or emergency ending of method execution
• flexible filtering Throwable types for logging
• configurable verbosity based on the enabled log level
• pre-defined printers to log arguments or method return value in different formats:
  • JSON (by Jackson)
  • XML (by JAXB)
• declarative defining (with SpEL) and erasing of Mapped Diagnostic Context (MDC) based on scopes
• multiple logger definition
• annotations validation during application context start
• ability to use meta-annotations (applied to other annotations) and annotated method overriding
• manual logging with invoker class detection is also available

Eclair logs annotated Methods and Parameters only.
Implementation is based on standard Spring proxying with all its consequences and limitations.

Annotated Method is able to log beginning and ending (except the emergency ending) of execution.
Works the same as both @Log.in and @Log.out annotations with all matching attribute values.
Note: emergency ending of the method execution should be specified separately by @Log.error annotation.

Can be defined on Parameter and specify logging settings for it.

Should have unique logger value per annotated element.
Parameter-level annotation has higher priority settings than Method-level with same logger value.

See also @Log.in, @Log.out and @Log.error annotations and their specific attributes

Defines MDC (Mapped Diagnostic Context) entry. MDC is level-insensitive.
Before method execution beginning, @Mdc will be processed first and after ending cleared last.
So annotations @Log / @Log.in / @Log.out of the same method will be processed inside @Mdc processing.

Eclair compatible with Java 8, Spring Boot 1.5.0+.

Add this to your POM:

<dependency>
    <groupId>ru.tinkoff</groupId>
    <artifactId>eclair-spring-boot-starter</artifactId>
    <version>0.9.0</version>
</dependency>

The examples assume that you are using a standard SimpleLogger and that you have the following configuration property:

logging.pattern.console: %d{yyyy-MM-dd HH:mm:ss.SSS UTC} [%thread] %-5level [%X] %logger{35} %msg%n

All available log levels in order from the most common TRACE to the rarest OFF:

• OFF deactivates logging completely
• ERROR and FATAL are identical (ERROR is used everywhere)

TRACE > DEBUG > INFO > WARN > ERROR = FATAL > OFF

Used Spring Boot log levels enum: org.springframework.boot.logging.LogLevel

The left table column shows the configured available logging level for the current method.
The right column shows a log sample or the specified level.

DEBUG level by default.

@Log
void simple() {
}

@Log(INFO)
boolean verbose(String s, Integer i, Double d) {
    return false;
}

You can specify printer's bean name or alias.

@Log(printer = "jaxb2Printer")
void verboseXml(Dto dto, Integer i) {
}

Errors can be filtered multiple times by ofType and exclude attributes.
By default ofType contains Throwable and includes all subtypes.
If the thrown exception matches any of @Log.error filters it will be logged according to the settings of the corresponding annotation.

@Log.error(level = WARN, ofType = {NullPointerException.class, IndexOutOfBoundsException.class})
@Log.error(exclude = Error.class)
void filterErrors(Throwable throwable) throws Throwable {
    throw throwable;
}

filterErrors(new NullPointerException());
filterErrors(new Exception());
filterErrors(new Error());

Note: If method is not annotated, log string will have the highest level among annotated parameters.
Note: Parameter name printed for TRACE and DEBUG levels by default.

void parameter(@Log(INFO) Dto dto, String s, Integer i) {
}

You can have several EclairLogger implementations in your application context.
This can be useful for logging various slices of information to different targets.

If logger attribute not defined, single candidate or @Primary bean will be used.

@Log
@Log(logger = "auditLogger")
void twoLoggers() {
}

MDC - Mapped Diagnostic Context

Key/value pair defined by annotation automatically cleared after exit from the method.
global MDC is available within ThreadLocal scope.
value attribute can contain SpEL expression and invoke static methods or beans by id from the application context.

Note: MDC is level-insensitive and printed every time.
Note: MDC does not guarantee order of elements when printing.

Before method execution beginning, @Mdc annotations will be processed first and after ending cleared last.
So annotations @Log / @Log.in / @Log.out of the same method will be processed inside @Mdc processing.

@Log
void outer() {
    self.mdc();
}

@Mdc(key = "static", value = "string")
@Mdc(key = "sum", value = "1 + 1", global = true)
@Mdc(key = "beanReference", value = "@jacksonPrinter.print(new ru.tinkoff.eclair.example.Dto())")
@Mdc(key = "staticMethod", value = "T(java.util.UUID).randomUUID()")
@Log
void mdc() {
    self.inner();
}

@Log.in
void inner() {
}

DEBUG [] r.t.eclair.example.Example.outer >
DEBUG [beanReference={"i":0,"s":null}, sum=2, static=string, staticMethod=01234567-89ab-cdef-ghij-klmnopqrstuv] r.t.eclair.example.Example.mdc >
DEBUG [beanReference={"i":0,"s":null}, sum=2, static=string, staticMethod=01234567-89ab-cdef-ghij-klmnopqrstuv] r.t.eclair.example.Example.inner >
DEBUG [beanReference={"i":0,"s":null}, sum=2, static=string, staticMethod=01234567-89ab-cdef-ghij-klmnopqrstuv] r.t.eclair.example.Example.mdc <
DEBUG [sum=2] r.t.eclair.example.Example.outer <

MDC can get access to annotated parameter value with SpEL as root object of evaluation context.

@Log.in
void mdcByArgument(@Mdc(key = "dto", value = "#this")
                   @Mdc(key = "length", value = "s.length()") Dto dto) {
}

DEBUG [length=8, dto=Dto{i=12, s='password'}] r.t.e.example.Example.mdcByArgument > dto=Dto{i=12, s='password'}

Inject ManualLogger implementation for manual logging.

If execution time is important to you, manual logging with ManualLogger is not recommended.

Expensive calculations may be wrapped into Supplier for lazy initialization.

@Autowired
private ManualLogger logger;

@Log
void manual() {
    logger.info("Eager logging: {}", Math.PI);
    logger.debug("Lazy logging: {}", (Supplier) () -> Math.PI);
}

19.05.2023 - 0.9.0 SpringBoot 3.0 support
21.01.2022 - 0.8.4 Make SimpleLogger more extendable
07.05.2018 - 0.8.3 Corrected optional classes usage in auto-configuration
06.05.2018 - 0.8.2 Published on Maven Central Repository
25.04.2018 - 0.8.1 Removed Lombok dependency
24.04.2018 - 0.8.0 Basic features

Copyright 2018 Tinkoff Bank
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

    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.