issue #23 添加日志输出功能，使用了slf4j

pom.xml

@@ -42,9 +42,21 @@
     <downloadJavadocs>true</downloadJavadocs>
     <downloadSources>true</downloadSources>
     <httpclient.version>4.3.5</httpclient.version>
+    <slf4j.version>1.7.10</slf4j.version>
   </properties>
 
   <dependencies>
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-api</artifactId>
+      <version>${slf4j.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-simple</artifactId>
+      <version>${slf4j.version}</version>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>org.apache.httpcomponents</groupId>
       <artifactId>fluent-hc</artifactId>

weixin-java-common/src/main/java/me/chanjar/weixin/common/session/SessionManagerImpl.java

@@ -1,12 +1,16 @@
 package me.chanjar.weixin.common.session;
 
 import me.chanjar.weixin.common.util.res.StringManager;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
 public class SessionManagerImpl implements WxSessionManager, InternalSessionManager {
 
+  protected final Logger log = LoggerFactory.getLogger(SessionManagerImpl.class);
+
   protected static final StringManager sm =
       StringManager.getManager(Constants.Package);
 
@@ -226,7 +230,7 @@ public class SessionManagerImpl implements WxSessionManager, InternalSessionMana
     int expireHere = 0 ;
 
     if(log.isDebugEnabled())
-      log.debug("Start expire sessions " + getName() + " at " + timeNow + " sessioncount " + sessions.length);
+      log.debug("Start expire sessions {} at {} sessioncount {}", getName(), timeNow, sessions.length);
     for (int i = 0; i < sessions.length; i++) {
       if (sessions[i]!=null && !sessions[i].isValid()) {
         expireHere++;
@@ -234,7 +238,7 @@ public class SessionManagerImpl implements WxSessionManager, InternalSessionMana
     }
     long timeEnd = System.currentTimeMillis();
     if(log.isDebugEnabled())
-      log.debug("End expire sessions " + getName() + " processingTime " + (timeEnd - timeNow) + " expired sessions: " + expireHere);
+      log.debug("End expire sessions {} processingTime {} expired sessions: {}", getName(), timeEnd - timeNow, expireHere);
     processingTime += ( timeEnd - timeNow );
 
   }

weixin-java-cp/src/main/java/me/chanjar/weixin/cp/api/WxCpServiceImpl.java

@@ -34,6 +34,8 @@ import org.apache.http.impl.client.BasicCredentialsProvider;
 import org.apache.http.impl.client.BasicResponseHandler;
 import org.apache.http.impl.client.CloseableHttpClient;
 import org.apache.http.impl.client.HttpClients;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.io.File;
 import java.io.IOException;
@@ -45,6 +47,8 @@ import java.util.concurrent.atomic.AtomicBoolean;
 
 public class WxCpServiceImpl implements WxCpService {
 
+  protected final Logger log = LoggerFactory.getLogger(WxCpServiceImpl.class);
+
   /**
    * 全局的是否正在刷新access token的锁
    */
@@ -380,7 +384,7 @@ public class WxCpServiceImpl implements WxCpService {
         if (error.getErrorCode() == -1) {
           int sleepMillis = retrySleepMillis * (1 << retryTimes);
           try {
-            System.out.println("微信系统繁忙，" + sleepMillis + "ms后重试(第" + (retryTimes + 1) + "次)");
+            log.debug("微信系统繁忙，{}ms 后重试(第{}次)", sleepMillis, retryTimes + 1);
             Thread.sleep(sleepMillis);
           } catch (InterruptedException e1) {
             throw new RuntimeException(e1);

weixin-java-mp/src/main/java/me/chanjar/weixin/mp/api/WxMpServiceImpl.java

@@ -31,6 +31,8 @@ import org.apache.http.impl.client.BasicCredentialsProvider;
 import org.apache.http.impl.client.BasicResponseHandler;
 import org.apache.http.impl.client.CloseableHttpClient;
 import org.apache.http.impl.client.HttpClients;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.io.File;
 import java.io.IOException;
@@ -42,6 +44,8 @@ import java.util.UUID;
 
 public class WxMpServiceImpl implements WxMpService {
 
+  protected final Logger log = LoggerFactory.getLogger(WxMpServiceImpl.class);
+
   /**
    * 全局的是否正在刷新access token的锁
    */
@@ -462,7 +466,7 @@ public class WxMpServiceImpl implements WxMpService {
         if (error.getErrorCode() == -1) {
           int sleepMillis = retrySleepMillis * (1 << retryTimes);
           try {
-            System.out.println("微信系统繁忙，" + sleepMillis + "ms后重试(第" + (retryTimes + 1) + "次)");
+            log.debug("微信系统繁忙，{}ms 后重试(第{}次)", sleepMillis, retryTimes + 1);
             Thread.sleep(sleepMillis);
           } catch (InterruptedException e1) {
             throw new RuntimeException(e1);