整合druid的配置：
在pom.xml中：
com.alibaba druid-spring-boot-starter 1.1.23 在application.yml中：
spring: datasource: druid: url: jdbc:mysql://localhost:3307/shopping?useSSl=false&&allowMultiQueries=true&useAffectedRows=true #数据库地址 username: root #用户名 password: 123456 #密码 max-active: 20 #连接池最大值 initial-size: 5 #连接池初始值 min-idle: 5 #连接池最小空值 min-evictable-idle-time-millis: 300000 max-wait: 60000 #最大等待时间 validation-query: select 1 # 检测连接是否有效时执行的sql命令 test-on-borrow: false # 借用连接时执行validationQuery检测连接是否有效，做了这个配置会降低性能 test-on-return: false #归还连接时执行validationQuery检测连接是否有效，做了这个配置会降低性能 test-while-idle: true # 连接空闲时检测，如果连接空闲时间大于timeBetweenEvictionRunsMillis指定的毫秒，执行validationQuery指定的SQL来检测连接是否有效 time-between-eviction-runs-millis: 60000 # 空闲连接检查、废弃连接清理、空闲连接池大小调整的操作时间间隔，单位是毫秒(1分钟) #监控有关的配置↓ filters: stat,wall # 配置监控统计拦截的filters，去掉后监控界面sql无法统计，'wall'用于防火墙 connection-properties: druid.stat.mergeSql: true filter: stat: slow-sql-millis: 500 web-stat-filter: enabled: true #是否启用StatFilter,默认值false，用于采集 web-jdbc 关联监控的数据。 url-pattern: /* # 需要监控的url exclusions: /druid/*,*.js,*.gif,*.jpg,*.png,*.css,*.ico #是否启用StatFilter默认值false，用于采集 web-jdbc 关联监控的数据。 stat-view-servlet: enabled: true #启用sql监控服务 url-pattern: /druid/* reset-enable: false login-username: admin login-password: 123456
但是在运行之后，成功获取到数据，但是后台却报了错误:discard long time none received connection. , jdbcUrl:jdbc:mysql://localhost:3306/XXX 这是怎么一回事呢？以前的版本并不会有这样的问题，
发现报错的来源是：这个package com.alibaba.druid.pool 里的这个方法：
protected boolean testConnectionInternal(DruidConnectionHolder holder, Connection conn) { String sqlFile = JdbcSqlStat.getContextSqlFile(); String sqlName = JdbcSqlStat.getContextSqlName(); if (sqlFile != null) { JdbcSqlStat.setContextSqlFile((String)null); } if (sqlName != null) { JdbcSqlStat.setContextSqlName((String)null); } boolean var6; try { boolean valid; if (this.validConnectionChecker == null) { if (conn.isClosed()) { valid = false; return valid; } if (null == this.validationQuery) { valid = true; return valid; } Statement stmt = null; ResultSet rset = null; boolean var7; try { stmt = conn.createStatement(); if (this.getValidationQueryTimeout() > 0) { stmt.setQueryTimeout(this.validationQueryTimeout); } rset = stmt.executeQuery(this.validationQuery); if (!rset.next()) { var7 = false; return var7; } } finally { JdbcUtils.close(rset); JdbcUtils.close(stmt); } if (this.onFatalError) { this.lock.lock(); try { if (this.onFatalError) {this.onFatalError = false; } } finally { this.lock.unlock(); } } var7 = true; return var7; } valid = this.validConnectionChecker.isValidConnection(conn, this.validationQuery, this.validationQueryTimeout); long currentTimeMillis = System.currentTimeMillis(); if (holder != null) { holder.lastValidTimeMillis = currentTimeMillis; holder.lastExecTimeMillis = currentTimeMillis; } if (valid && this.isMySql) { long lastPacketReceivedTimeMs = MySqlUtils.getLastPacketReceivedTimeMs(conn); //获取mysql上次使用的时间 if (lastPacketReceivedTimeMs > 0L) { long mysqlIdleMillis = currentTimeMillis - lastPacketReceivedTimeMs; if (lastPacketReceivedTimeMs > 0L && mysqlIdleMillis >= this.timeBetweenEvictionRunsMillis) { this.discardConnection(holder); String errorMsg = "discard long time none received connection. , jdbcUrl : " + this.jdbcUrl + ", jdbcUrl : " + this.jdbcUrl + ", lastPacketReceivedIdleMillis : " + mysqlIdleMillis; LOG.error(errorMsg);//想来error应该就是这里发出来的吧 boolean var13 = false; return var13; } } } if (valid && this.onFatalError) { this.lock.lock(); try { if (this.onFatalError) { this.onFatalError = false; } } finally { this.lock.unlock(); } } boolean var46 = valid; return var46; } catch (Throwable var41) { var6 = false; } finally { if (sqlFile != null) { JdbcSqlStat.setContextSqlFile(sqlFile); } if (sqlName != null) { JdbcSqlStat.setContextSqlName(sqlName); } } return var6; } public Set getActiveConnections() { this.activeConnectionLock.lock(); HashSet var1; try { var1 = new HashSet(this.activeConnections.keySet()); } finally { this.activeConnectionLock.unlock(); } return var1; } this.timeBetweenEvictionRunsMillis 我们是 60000ms 也就是1分钟，是空闲连接检查，如果超过了1分钟，就discardConnection(holder); 和LOG.error(errorMsg);//error是这里发出来的,之后我们发现，在前面还有一个条件。if (valid && this.isMySql) ，我们设置valid为false即可。
找一下valid有什么来源
//// Source code recreated from a .class file by IntelliJ IDEA// (powered by FernFlower decompiler)//package com.alibaba.druid.pool.vendor;import com.alibaba.druid.pool.DruidPooledConnection;import com.alibaba.druid.pool.ValidConnectionChecker;import com.alibaba.druid.pool.ValidConnectionCheckerAdapter;import com.alibaba.druid.proxy.jdbc.ConnectionProxy;import com.alibaba.druid.support.logging.Log;import com.alibaba.druid.support.logging.LogFactory;import com.alibaba.druid.util.JdbcUtils;import com.alibaba.druid.util.Utils;import java.io.Serializable;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.sql.Connection;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.Properties;public class MySqlValidConnectionChecker extends ValidConnectionCheckerAdapter implements ValidConnectionChecker, Serializable { public static final int DEFAULT_VALIDATION_QUERY_TIMEOUT = 1; public static final String DEFAULT_VALIDATION_QUERY = "SELECT 1"; private static final long serialVersionUID = 1L; private static final Log LOG = LogFactory.getLog(MySqlValidConnectionChecker.class); private Class clazz; private Method ping; private boolean usePingMethod = false; public MySqlValidConnectionChecker() { try { this.clazz = Utils.loadClass("com.mysql.jdbc.MySQLConnection"); if (this.clazz == null) { this.clazz = Utils.loadClass("com.mysql.cj.jdbc.ConnectionImpl"); } if (this.clazz != null) { this.ping = this.clazz.getMethod("pingInternal", Boolean.TYPE, Integer.TYPE); } if (this.ping != null) { this.usePingMethod = true; } } catch (Exception var2) { LOG.warn("Cannot resolve com.mysql.jdbc.Connection.ping method. Will use 'SELECT 1' instead.", var2); } this.configFromProperties(System.getProperties()); } public void configFromProperties(Properties properties) { String property = properties.getProperty("druid.mysql.usePingMethod"); if ("true".equals(property)) { this.setUsePingMethod(true); } else if ("false".equals(property)) { this.setUsePingMethod(false); } } public boolean isUsePingMethod() { return this.usePingMethod; } public void setUsePingMethod(boolean usePingMethod) { this.usePingMethod = usePingMethod; }//这里就是决定valid取值的方法 public boolean isValidConnection(Connection conn, String validateQuery, int validationQueryTimeout) throws Exception { if (conn.isClosed()) { return false; } else { if (this.usePingMethod) {//可以设置它false」让验证空闲连接使用 select 1，而不是使用MySQL的Ping，这样就刷新了上次使用时间，不会出现空闲 60秒以上的连接 if (conn instanceof DruidPooledConnection) { conn = ((DruidPooledConnection)conn).getConnection(); } if (conn instanceof ConnectionProxy) { conn = ((ConnectionProxy)conn).getRawObject(); } if (this.clazz.isAssignableFrom(conn.getClass())) { if (validationQueryTimeout <= 0) { validationQueryTimeout = 1; } try { this.ping.invoke(conn, true, validationQueryTimeout * 1000); return true; } catch (InvocationTargetException var11) { Throwable cause = var11.getCause(); if (cause instanceof SQLException) {throw (SQLException)cause; } throw var11; } } } String query = validateQuery; if (validateQuery == null || validateQuery.isEmpty()) { query = "SELECT 1"; } Statement stmt = null; ResultSet rs = null; boolean var7; try { stmt = conn.createStatement(); if (validationQueryTimeout > 0) { stmt.setQueryTimeout(validationQueryTimeout); } rs = stmt.executeQuery(query); var7 = true; } finally { JdbcUtils.close(rs); JdbcUtils.close(stmt); } return var7; } }}mysql数据库有一个wait_timeout的配置，默认值为28800(即8小时).在默认配置不改变的情况下，如果连续8小时内数据库空闲的话，就会关闭空闲的连接，而druid是1分钟就断开，主要为了提高数据库的处理能力。我们让验证空闲连接使用 select 1，而不是使用MySQL的Ping。
static { System.setProperty("druid.mysql.usePingMethod","false"); }加入这个就好了，不适用PingMethod
来源地址：https://blog.csdn.net/m0_54409739/article/details/129261025
