Communications link failure,The error may involve defaultParameterMap的问题【已解决】

查阅资料得知是连接池问题，把c3p0或dbcp改为druid即可解决。
下面附上上druid配置过程

druid依赖

<!-- SPRINGBOOT DRUID -->
		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>druid</artifactId>
			<version>1.1.12</version>
		</dependency>

整体pom

<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
			<exclusions>
				<exclusion>
					<groupId>org.junit.vintage</groupId>
					<artifactId>junit-vintage-engine</artifactId>
				</exclusion>
			</exclusions>
		</dependency>
		<!-- SPRINGBOOT DRUID -->
		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>druid</artifactId>
			<version>1.1.12</version>
		</dependency>

		<!-- mysql-->
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>5.1.3</version>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-jdbc</artifactId>
		</dependency>
		<dependency>
			<groupId>org.mybatis.spring.boot</groupId>
			<artifactId>mybatis-spring-boot-starter</artifactId>
			<version>1.3.2</version>
		</dependency>
		<dependency>
			<groupId>com.squareup.okhttp3</groupId>
			<artifactId>okhttp</artifactId>
		</dependency>
		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>fastjson</artifactId>
			<version>1.2.60</version>
		</dependency>
		<!-- 文件上传 -->
		<dependency>
			<groupId>commons-fileupload</groupId>
			<artifactId>commons-fileupload</artifactId>
			<version>1.3.2</version>
		</dependency>
		<!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
		<dependency>
			<groupId>commons-io</groupId>
			<artifactId>commons-io</artifactId>
			<version>2.5</version>
		</dependency>
		<!-- https://mvnrepository.com/artifact/org.mybatis.generator/mybatis-generator-core -->
		<dependency>
			<groupId>org.mybatis.generator</groupId>
			<artifactId>mybatis-generator-core</artifactId>
			<version>1.3.7</version>
		</dependency>
	</dependencies>

DruidConfig.java

@Configuration//在项目启动时可以初始化配置
public class DruidConfig {
    @Bean
    public ServletRegistrationBean staViewServlet(){
        ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean(new StatViewServlet(),
                "/druid/*");
        //白名单为空允许任何ip访问
        servletRegistrationBean.addInitParameter("allow","127.0.0.1");
        //ip黑名单(存在共同时，deny优先于allow)：如果满足deny的即提示：Sorry you are not permitted...
        servletRegistrationBean.addInitParameter("deny","127.0.0.2");
        //登录查看信息的账号密码
        servletRegistrationBean.addInitParameter("loginUsername","druid");
        servletRegistrationBean.addInitParameter("loginPassword","druid");
        //是否能够重置数据
        servletRegistrationBean.addInitParameter("resetEnable","true");
        return servletRegistrationBean;
    }

    @Bean
    public FilterRegistrationBean statFilter(){
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(new WebStatFilter());
        //添加过滤规则
        filterRegistrationBean.addUrlPatterns("/*");
        //添加不需要忽略的格式信息
        filterRegistrationBean.addInitParameter("exclusions","*.js,*.gif,*.jpn,*.png,*.css,*.ico,/druid/*");
        return filterRegistrationBean;
    }

    //配置数据库的基本连接信息
    @Bean
    @Primary
    @ConfigurationProperties(prefix = "spring.datasource")//在application.properties中读取配置信息注入到DruidDataSource里
    public DataSource dataSource(){
        DruidDataSource druidDataSource = DataSourceBuilder.create().type(DruidDataSource.class).build();
        druidDataSource.setInitialSize(3);//初始化物理连接的数量
        try {
            druidDataSource.addFilters("stat,wall");//stat是sql监控，wall是防火墙(如果不添加则监控无效)，不能添加log4j不然会出错
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return druidDataSource;
    }

}

application.yml

spring:
  datasource:
      url: xxx
      username: root
      password: root
      driver-class-name: com.mysql.jdbc.Driver
      type: com.alibaba.druid.pool.DruidDataSource

经过以上步骤，问题解决