以下为自己刚学习java遇到及排错过程
日志换成了 slf4j+logback,没看到本地有日志文件生成，调试时发现有错误提示(是在加载druid时出现的):
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder". SLF4J: Defaulting to no-operation (NOP) logger implementation SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
网上说没有配置实际的日志实现包导致，但在pom.xml中是有配置的:
<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.26</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
<version>1.2.3</version>
</dependency>
<!-- https://mvnrepository.com/artifact/ch.qos.logback/logback-classic -->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
<scope>test</scope> // 注意此处
</dependency>
找到出错的源码:comalibabadruid1.1.16druid-1.1.16-sources.jar!comalibabadruidpoolDruidAbstractDataSource.java
public abstract class DruidAbstractDataSource extends WrapperAdapter
implements DruidAbstractDataSourceMBean, DataSource, DataSourceProxy, Serializable
{
private static final long serialVersionUID = 1L;
private final static Log LOG = LogFactory.getLog(DruidAbstractDataSource.class); // 此处
...
}
comalibabadruid1.1.16druid-1.1.16-sources.jar!comalibabadruidsupportloggingLogFactory.java
public class LogFactory {
private static Constructor logConstructor;
static {
String logType= System.getProperty("druid.logType");
if(logType != null){
if(logType.equalsIgnoreCase("slf4j")){
tryImplementation("org.slf4j.Logger", "com.alibaba.druid.support.logging.SLF4JImpl");
}else if(logType.equalsIgnoreCase("log4j")){
tryImplementation("org.apache.log4j.Logger", "com.alibaba.druid.support.logging.Log4jImpl");
}else if(logType.equalsIgnoreCase("log4j2")){
tryImplementation("org.apache.logging.log4j.Logger", "com.alibaba.druid.support.logging.Log4j2Impl");
}else if(logType.equalsIgnoreCase("commonsLog")){
tryImplementation("org.apache.commons.logging.LogFactory",
"com.alibaba.druid.support.logging.JakartaCommonsLoggingImpl");
}else if(logType.equalsIgnoreCase("jdkLog")){
tryImplementation("java.util.logging.Logger", "com.alibaba.druid.support.logging.Jdk14LoggingImpl");
}
}
// 优先选择log4j,而非Apache Common Logging. 因为后者无法设置真实Log调用者的信息
tryImplementation("org.slf4j.Logger", "com.alibaba.druid.support.logging.SLF4JImpl"); // 此处
tryImplementation("org.apache.log4j.Logger", "com.alibaba.druid.support.logging.Log4jImpl");
tryImplementation("org.apache.logging.log4j.Logger", "com.alibaba.druid.support.logging.Log4j2Impl");
tryImplementation("org.apache.commons.logging.LogFactory",
"com.alibaba.druid.support.logging.JakartaCommonsLoggingImpl");
tryImplementation("java.util.logging.Logger", "com.alibaba.druid.support.logging.Jdk14LoggingImpl");
if (logConstructor == null) {
try {
logConstructor = NoLoggingImpl.class.getConstructor(String.class);
} catch (Exception e) {
throw new IllegalStateException(e.getMessage(), e);
}
}
}
}
private static void tryImplementation(String testClassName, String implClassName) {
if (logConstructor != null) {
return;
}
try {
Resources.classForName(testClassName);
Class implClass = Resources.classForName(implClassName);
logConstructor = implClass.getConstructor(new Class[] { String.class });
Class<?> declareClass = logConstructor.getDeclaringClass();
if (!Log.class.isAssignableFrom(declareClass)) {
logConstructor = null;
}
try {
if (null != logConstructor) {
logConstructor.newInstance(LogFactory.class.getName()); // 此处
}
} catch (Throwable t) {
logConstructor = null;
}
} catch (Throwable t) {
// skip
}
}
comalibabadruid1.1.16druid-1.1.16-sources.jar!comalibabadruidsupportloggingSLF4JImpl.java
public class SLF4JImpl implements Log {
private static final String callerFQCN = SLF4JImpl.class.getName();
private static final Logger testLogger = LoggerFactory.getLogger(SLF4JImpl.class); // 此处
static {
// if the logger is not a LocationAwareLogger instance, it can not get correct stack StackTraceElement
// so ignore this implementation.
if (!(testLogger instanceof LocationAwareLogger)) {
throw new UnsupportedOperationException(testLogger.getClass() + " is not a suitable logger");
}
}
...
}
orgslf4jslf4j-api1.7.26slf4j-api-1.7.26-sources.jar!orgslf4jLoggerFactory.java
public static Logger getLogger(Class<?> clazz) {
Logger logger = getLogger(clazz.getName()); // 此处
if (DETECT_LOGGER_NAME_MISMATCH) {
Class<?> autoComputedCallingClass = Util.getCallingClass();
if (autoComputedCallingClass != null && nonMatchingClasses(clazz, autoComputedCallingClass)) {
Util.report(String.format("Detected logger name mismatch. Given name: "%s"; computed name: "%s".", logger.getName(),
autoComputedCallingClass.getName()));
Util.report("See " + LOGGER_NAME_MISMATCH_URL + " for an explanation");
}
}
return logger;
}
public static Logger getLogger(String name) {
ILoggerFactory iLoggerFactory = getILoggerFactory(); // 此处
return iLoggerFactory.getLogger(name);
}
public static ILoggerFactory getILoggerFactory() {
if (INITIALIZATION_STATE == UNINITIALIZED) {
synchronized (LoggerFactory.class) {
if (INITIALIZATION_STATE == UNINITIALIZED) {
INITIALIZATION_STATE = ONGOING_INITIALIZATION;
performInitialization(); // 此处
}
}
}
switch (INITIALIZATION_STATE) {
case SUCCESSFUL_INITIALIZATION:
return StaticLoggerBinder.getSingleton().getLoggerFactory();
case NOP_FALLBACK_INITIALIZATION:
return NOP_FALLBACK_FACTORY;
case FAILED_INITIALIZATION:
throw new IllegalStateException(UNSUCCESSFUL_INIT_MSG);
case ONGOING_INITIALIZATION:
// support re-entrant behavior.
// See also http://jira.qos.ch/browse/SLF4J-97
return SUBST_FACTORY;
}
throw new IllegalStateException("Unreachable code");
}
private final static void performInitialization() {
bind(); // 此处
if (INITIALIZATION_STATE == SUCCESSFUL_INITIALIZATION) {
versionSanityCheck();
}
}
private final static void bind() {
try {
...
// skip check under android, see also
// http://jira.qos.ch/browse/SLF4J-328
if (!isAndroid()) {
staticLoggerBinderPathSet = findPossibleStaticLoggerBinderPathSet(); // 此处
reportMultipleBindingAmbiguity(staticLoggerBinderPathSet);
}
...
} catch () {
...
}
}
static Set<URL> findPossibleStaticLoggerBinderPathSet() {
// use Set instead of list in order to deal with bug #138
// LinkedHashSet appropriate here because it preserves insertion order
// during iteration
Set<URL> staticLoggerBinderPathSet = new LinkedHashSet<URL>();
try {
ClassLoader loggerFactoryClassLoader = LoggerFactory.class.getClassLoader();
Enumeration<URL> paths;
if (loggerFactoryClassLoader == null) {
paths = ClassLoader.getSystemResources(STATIC_LOGGER_BINDER_PATH);
} else {
paths = loggerFactoryClassLoader.getResources(STATIC_LOGGER_BINDER_PATH);
}
while (paths.hasMoreElements()) {
URL path = paths.nextElement();
staticLoggerBinderPathSet.add(path);
}
} catch (IOException ioe) {
...
}
return staticLoggerBinderPathSet; // 返回的size为零
}
找到生成目录，缺少 logback-classic-1.2.3.jar
最终发现是因为pom.xml中影响(这段代码直接从maven复制)
最终是此句影响，还是基础不劳呀