druid源码解读

druid源码解读

拉取代码

git clone .git

编译代码（跳过test）

mvn clean install -st.skip=true

集成demo项目pom文件

<dependency><groupId>com.alibaba</groupId><artifactId>druid</artifactId><version>1.2.8</version>
</dependency>
<!--自启动Druid管理后台-->
<dependency><groupId>com.alibaba</groupId><artifactId>druid-spring-boot-starter</artifactId><version>1.2.8</version>
</dependency>

druid的配置参数配置

# 数据库配置
spring:datasource:type: com.alibaba.druid.pool.DruidDataSourcedruid:url: jdbc:mysql://127.0.0.1:3306/jk_test?allowMultiQueries=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai&useSSL=false&autoReconnect=true&nullCatalogMeansCurrent=trueusername: rootpassword: 12345678driverClassName: sql.cj.jdbc.Driver#初始化连接initial-size: 10#最大活动连接max-active: 100#最小连接池数量min-idle: 10#从池中取连接的最大等待时间，单位ms.max-wait: 60000#开启池的prepared（默认是false，未调整，经过测试，开启后的性能没有关闭的好。）pool-prepared-statements: truemax-pool-prepared-statement-per-connection-size: 20#每n秒运行一次空闲连接回收器time-between-eviction-runs-millis: 60000#池中的连接空闲..后被回收min-evictable-idle-time-millis: 300000#验证使用的SQL语句validation-query: SELECT 1 FROM DUAL# 指明连接是否被空闲连接回收器(如果有)进行检验.如果检测失败,则连接将被从池中去除.test-while-idle: true#借出连接时不要测试，否则很影响性能test-on-borrow: falsetest-on-return: falsestat-view-servlet:enabled: trueurl-pattern: /druid/*#login-username: admin#login-password: adminfilter:stat:log-slow-sql: trueslow-sql-millis: 1000merge-sql: truewall:config:multi-statement-allow: true#连接泄漏回收参数，当可用连接数少于3个时才执行,超过时间限制，回收没有用(废弃)的连接（默认为 300秒，调整为180）#getNumIdle() < 2) and (getNumActive() > getMaxActive() - 3)remove-abandoned: true# 连接泄漏回收参数，180秒，泄露的连接可以被删除的超时值remove-abandoned-timeout: 3000# abanded连接时输出错误日志logAbandoned: true

demo代码地址

durid源码参数配置的作用和代码块分析

initial-size: 10

#初始化连接

//DruidDataSource中 448 
{String property = Property("druid.initialSize");if (property != null && property.length() > 0) {try {int value = Integer.parseInt(property);this.setInitialSize(value);} catch (NumberFormatException e) {("illegal property 'druid.initialSize'", e);}}
}
// 初始化链接需要小于最大活动连接数量
if (getInitialSize() > maxActive) {throw new IllegalArgumentException("illegal initialSize " + this.initialSize + ", maxActive " + maxActive);
}

max-active: 100

#最大活动连接

//DruidDataSource中 470
{String property = Property("druid.maxActive");if (property != null && property.length() > 0) {try {int value = Integer.parseInt(property);this.setMaxActive(value);} catch (NumberFormatException e) {("illegal property 'druid.maxActive'", e);}}}// 设置最大活动连接的代码
lock.lock();
try {// 获取总的活动数量 int allCount = this.poolingCount + this.activeCount;// maxActive 和 allCount 取大的那个 TODO 疑问点，为什么还需要比较all count init的时候初始化直接获取最大的maxActive不就好了吗？是基于配置中心动态配置最大活动数量的考虑吗？if (maxActive > allCount) {tions = tions, maxActive);evictConnections = new DruidConnectionHolder[maxActive];keepAliveConnections = new DruidConnectionHolder[maxActive];} else {tions = tions, allCount);evictConnections = new DruidConnectionHolder[allCount];keepAliveConnections = new DruidConnectionHolder[allCount];}
​this.maxActive = maxActive;
} finally {lock.unlock();
}

min-idle: 10

#最小连接池数量

// 最小连接池的数量
{String property = Property("druid.minIdle");if (property != null && property.length() > 0) {try {int value = Integer.parseInt(property);this.setMinIdle(value);} catch (NumberFormatException e) {("illegal property 'druid.minIdle'", e);}}
}
// 最大活动连接比较if (inited && value > this.maxActive) {throw new IllegalArgumentException("minIdle greater than maxActive, " + maxActive + " < " + this.minIdle);}

max-wait: 60000

#从池中取连接的最大等待时间，单位ms.

{String property = Property("druid.maxWait");if (property != null && property.length() > 0) {try {int value = Integer.parseInt(property);this.setMaxWait(value);} catch (NumberFormatException e) {("illegal property 'druid.maxWait'", e);}}
}
@Override
public DruidPooledConnection getConnection() throws SQLException {return getConnection(maxWait);
}
​
//创建连接的时候需要传入最大等待时长
public DruidPooledConnection getConnection(long maxWaitMillis) throws SQLException {init();
​if (filters.size() > 0) {FilterChainImpl filterChain = new FilterChainImpl(this);return filterChain.dataSource_connect(this, maxWaitMillis);} else {return getConnectionDirect(maxWaitMillis);}
}
// 最大等待时间放与 waitNanosLocal
// final long nanos = Nanos(maxWait);
// waitNanosLocal.set(nanos - estimate);

pool-prepared-statements: true

#开启池的prepared（默认是false，未调整，经过测试，开启后的性能没有关闭的好。）

{Boolean value = getBoolean(properties, "druid.poolPreparedStatements");if (value != null) {this.setPoolPreparedStatements0(value);}
}
// 是否缓存preparedStatement，也就是PSCache。PSCache对支持游标的数据库性能提升巨大，比如说oracle。在mysql下建议关闭。
if (this.isPoolPreparedStatements()) {buf.append("nn[");for (int i = 0; i < poolingCount; ++i) {DruidConnectionHolder conn = connections[i];if (conn != null) {if (i != 0) {buf.append(",");}buf.append("nt{ntID:");buf.append(System.Connection()));PreparedStatementPool pool = StatementPool();
​buf.append(", ntpoolStatements:[");
​int entryIndex = 0;try {for (Map.Entry<PreparedStatementKey, PreparedStatementHolder> entry : Map().entrySet()) {if (entryIndex != 0) {buf.append(",");}buf.append("ntt{hitCount:");buf.Value().getHitCount());buf.append(",sql:"");buf.Key().getSql());buf.append(""");buf.append("t}");
​entryIndex++;}} catch (ConcurrentModificationException e) {// skip ..}
​buf.append("ntt]");
​buf.append("nt}");}}buf.append("n]");
}

max-pool-prepared-statement-per-connection-size: 20

#要启用PSCache，必须配置大于0，当大于0时，poolPreparedStatements自动触发修改为true。在Druid中，不会存在Oracle下PSCache占用内存过多的问题，可以把这个数值配置大一些，比如说100

public void setMaxPoolPreparedStatementPerConnectionSize(int maxPoolPreparedStatementPerConnectionSize) {
//为什么要设置大于0的时候开启poolPreparedStatements呢 直接开个参数或者直接true false不可以吗if (maxPoolPreparedStatementPerConnectionSize > 0) {this.poolPreparedStatements = true;} else {this.poolPreparedStatements = false;}
​this.maxPoolPreparedStatementPerConnectionSize = maxPoolPreparedStatementPerConnectionSize;
}// PreparedStatementPool 使用到这个参数，如果 <0 默认pool的 LRUCache map 为16 避免扩容？？
public PreparedStatementPool(DruidConnectionHolder holder){this.dataSource = DataSource();int initCapacity = DataSource().getMaxPoolPreparedStatementPerConnectionSize();if (initCapacity <= 0) {initCapacity = 16;}map = new LRUCache(initCapacity);
}

time-between-eviction-runs-millis: 60000

#每n秒运行一次空闲连接回收器

{String property = Property("druid.timeBetweenEvictionRunsMillis");if (property != null && property.length() > 0) {try {long value = Long.parseLong(property);this.setTimeBetweenEvictionRunsMillis(value);} catch (NumberFormatException e) {("illegal property 'druid.timeBetweenEvictionRunsMillis'", e);}}
}
// DuridDataSource#init判断保持连接的的时间小于最小的空闲时间 异常
if (keepAlive && keepAliveBetweenTimeMillis <= timeBetweenEvictionRunsMillis) {throw new SQLException("keepAliveBetweenTimeMillis must be grater than timeBetweenEvictionRunsMillis");
}
//当连接池初始化时，会初始化一个定时清除空闲连接的任务DestroyTask，该任务默认是1分钟执行一次（使用timeBetweenEvictionRunsMillis参数设置)
protected void createAndStartDestroyThread() {destroyTask = new DestroyTask();
​if (destroyScheduler != null) {//轮训销毁时间 定时清除空闲连接的任务long period = timeBetweenEvictionRunsMillis;if (period <= 0) {period = 1000;}destroySchedulerFuture = destroyScheduler.scheduleAtFixedRate(destroyTask, period, period,TimeUnit.MILLISECONDS);untDown();return;}
​String threadName = "Druid-ConnectionPool-Destroy-" + System.identityHashCode(this);destroyConnectionThread = new DestroyConnectionThread(threadName);destroyConnectionThread.start();
}

min-evictable-idle-time-millis: 300000

#池中的连接空闲..后被回收

{String property = Property("druid.minEvictableIdleTimeMillis");if (property != null && property.length() > 0) {try {long value = Long.parseLong(property);this.setMinEvictableIdleTimeMillis(value);} catch (NumberFormatException e) {("illegal property 'druid.minEvictableIdleTimeMillis'", e);}}
}
//定时清除空闲连接的任务， destroySchedulerFuture = destroyScheduler.scheduleAtFixedRate(destroyTask, period, period,                                                                    TimeUnit.MILLISECONDS);定时任务中会判断连接池的连接是否满足关闭的条件，如果满足则关闭，满足的条件如下：
​
//关闭条件，空闲时间大于minEvictableIdleTimeMillis，并且空闲连接大于minIdle，
// 其中checkCount为poolingCount - minIdle，即可能被关闭的连接数量
// 或者空闲时间大于maxEvictableIdleTimeMillis
​
if (idleMillis >= minEvictableIdleTimeMillis) {if (checkTime && i < checkCount) {evictConnections[evictCount++] = connection;continue;} else if (idleMillis > maxEvictableIdleTimeMillis) {evictConnections[evictCount++] = connection;continue;}
}