SpringBoot集成Druid连接池，Caused by: java.lang.ClassNotFoundException: org.apache.log4j

github：https://github.com/alibaba/druid

SpringBoot版本：1.5.9.RELEASE   默认使用的日志框架为log4j2

在配置 Druid 数据监控时，进行了如下配置

# 配置监控统计拦截的filters，去掉后监控界面sql将无法统计,'wall'用于防火墙
spring.datascoure.filters= stat, wall,log4j

filters: stat,wall,log4j

• stat：Druid内置提供一个StatFilter,用于统计监控信息。如果需要配置访问页面可以参考，https://github.com/alibaba/druid/wiki/%E9%85%8D%E7%BD%AE_StatViewServlet%E9%85%8D%E7%BD%AE
• wall：Druid防御SQL注入攻击的WallFilter就是通过Druid的SQL Parser分析。Druid提供的SQL Parser可以在JDBC层拦截SQL做相应处理，比如说分库分表、审计等。
• log4j：日志记录的功能，可以把sql语句打印到log4j2。

如上配置的使用log4j进行日志输入，而springboot框架使用的是log4j2，所以可将上面的log4j修改为log4j2,如下：

# 配置监控统计拦截的filters，去掉后监控界面sql将无法统计,'wall'用于防火墙
spring.datascoure.filters= stat, wall,log4j2

备注：如果没有配置filters的话，存在监控见面中的SQL监控没有数据的情况。因此需要添加如下配置：使其起作用后，才会报如上的错误。

package com.consmation.iwebmapserver.projectserver.config;

import com.alibaba.druid.pool.DruidDataSource;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

import javax.sql.DataSource;
import java.sql.SQLException;

@Configuration
@ConfigurationProperties(prefix="spring.datasources")
public class DruidDBConfig {
    private static Logger logger = LoggerFactory.getLogger(DruidDBConfig.class);

    @Value("${spring.datasource.url}")
    private String dbUrl;

    @Value("${spring.datasource.username}")
    private String username;

    @Value("${spring.datasource.password}")
    private String password;

    @Value("${spring.datasource.driver-class-name}")
    private String driverClassName;

    @Value("${spring.datasource.initialSize}")
    private int initialSize;

    @Value("${spring.datasource.minIdle}")
    private int minIdle;

    @Value("${spring.datasource.maxActive}")
    private int maxActive;

    @Value("${spring.datasource.maxWait}")
    private int maxWait;

    @Value("${spring.datasource.timeBetweenEvictionRunsMillis}")
    private int timeBetweenEvictionRunsMillis;

    @Value("${spring.datasource.minEvictableIdleTimeMillis}")
    private int minEvictableIdleTimeMillis;

    @Value("${spring.datasource.validationQuery}")
    private String validationQuery;

    @Value("${spring.datasource.testWhileIdle}")
    private boolean testWhileIdle;

    @Value("${spring.datasource.testOnBorrow}")
    private boolean testOnBorrow;

    @Value("${spring.datasource.testOnReturn}")
    private boolean testOnReturn;

    @Value("${spring.datasource.poolPreparedStatements}")
    private boolean poolPreparedStatements;

    @Value("${spring.datasource.maxPoolPreparedStatementPerConnectionSize}")
    private int maxPoolPreparedStatementPerConnectionSize;

    @Value("${spring.datasource.filters}")
    private String filters;

    @Value("{spring.datasource.connectionProperties}")
    private String connectionProperties;

    @Bean     //声明其为Bean实例
    @Primary  //在同样的DataSource中，首先使用被标注的DataSource
    public DataSource dataSource() {
        DruidDataSource datasource = new DruidDataSource();

        datasource.setUrl(this.dbUrl);
        datasource.setUsername(username);
        datasource.setPassword(password);
        datasource.setDriverClassName(driverClassName);

        //configuration
        datasource.setInitialSize(initialSize);
        datasource.setMinIdle(minIdle);
        datasource.setMaxActive(maxActive);
        datasource.setMaxWait(maxWait);
        datasource.setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis);
        datasource.setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis);
        datasource.setValidationQuery(validationQuery);
        datasource.setTestWhileIdle(testWhileIdle);
        datasource.setTestOnBorrow(testOnBorrow);
        datasource.setTestOnReturn(testOnReturn);
        datasource.setPoolPreparedStatements(poolPreparedStatements);
        datasource.setMaxPoolPreparedStatementPerConnectionSize(maxPoolPreparedStatementPerConnectionSize);
        try {
            datasource.setFilters(filters);
        } catch (SQLException e) {
           logger.error("druid configuration initialization filter", e);
        }
        datasource.setConnectionProperties(connectionProperties);

        return datasource;
    }
}