​在springboot相比于springmvc提供了一个极为重要的功能，就是自定义start（自定义jar包），同时spring也提供了一大波start。如spring-boot-starter-data-redis，spring-boot-starter-amqp。本文将教你如何自定义start。例子为从start中获取数据源。

1.自定义start能干什么

在架构考虑时，或许有一些通用方法抽取成start，在项目中使用时，直接引入即可。

2.创建自定义start

1.创建一个新的maven项目

创建一个普通的maven项目，作为start的开发环境

2.新建application.properties

在maven中创建application.properties文件。同时添加以下代码，作为常量配置。

login.className = com.mysql.jdbc.Driver
login.url=jdbc:mysql://localhost:3306/humanresource?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
login.user=root
login.password=root

3.创建LoginCheckProperties

创建类LoginCheckProperties，其中需要@ConfigurationProperties注解，prefix = “login” 的意思是调用项目中 ，application.properties中配置的参数。

@ConfigurationProperties(prefix = "login")
public class LoginCheckProperties {

    private String className;
    private String url;
    private String user;
    private String password;

    public String getClassName() {
        return className;
    }

    public void setClassName(String className) {
        this.className = className;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getUser() {
        return user;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

4.Config类

其中@EnableConfigurationProperties(LoginCheckProperties.class) 注解为固定写法，意义是实现自动配置上文中的Properties类。

@Configuration
@EnableConfigurationProperties(LoginCheckProperties.class)
@MapperScan(basePackages = MasterDataSourceConfig.PACKAGE, sqlSessionFactoryRef = "masterSqlSessionFactory")
public class MasterDataSourceConfig {

    // 精确到 master 目录，以便跟其他数据源隔离
    static final String PACKAGE = "com.airboot.bootdemo.dao.master";
    static final String MAPPER_LOCATION = "classpath*:mapper/master/*.xml";

    private String className;
    private String url;
    private String user;
    private String password;

    public MasterDataSourceConfig(LoginCheckProperties loginCheckProperties) {
        this.className = loginCheckProperties.getClassName();
        this.url = loginCheckProperties.getUrl();
        this.user = loginCheckProperties.getUser();
        this.password = loginCheckProperties.getPassword();
    }

    @Bean(name = "masterDataSource")
    public DataSource masterDataSource() {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(className);
        dataSource.setUrl(url);
        dataSource.setUsername(user);
        dataSource.setPassword(password);
        return dataSource;
    }

    @Bean(name = "masterTransactionManager")
    public DataSourceTransactionManager masterTransactionManager() {
        return new DataSourceTransactionManager(masterDataSource());
    }

    @Bean(name = "masterSqlSessionFactory")
    public SqlSessionFactory masterSqlSessionFactory(@Qualifier("masterDataSource") DataSource masterDataSource)
            throws Exception {
        final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
        sessionFactory.setDataSource(masterDataSource);
        sessionFactory.setMapperLocations(
                new PathMatchingResourcePatternResolver().getResources(MasterDataSourceConfig.MAPPER_LOCATION));
        return sessionFactory.getObject();
    }  
}

5.添加META-INF/spring.factories

最后在resources中新建文件夹META-INF，在其中建立文件spring.factories路径为上文Config中的路径。（需要向被引用者暴露）

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.*.*.*.*A,\
com.*.*.*.*B,\
com.*.*.*.*C,\
com.*.*.*.*D,\
com.*.*.*.*Util

6.显示start注释（选读）

如果想要在jar中加入注释 则需要在pom文件中修改以下代码 这样会生成一个 .jar 和一个:source.jar 需要将这两个jar包都加入项目中。

<build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-source-plugin</artifactId>
                <version>2.4</version>
                <configuration>
                    <aggregate>true</aggregate>
                </configuration>
                <executions>
                    <execution>
                        <id>attach-javadocs</id>
                        <goals>
                            <goal>jar</goal>
                        </goals>
                        <configuration>
                            <additionalparam>-Xdoclint:none</additionalparam>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

7.打包

使用命令mvn install。即可生成jar包。

8.引入jar包

       <dependency>
            <groupId>cn.baocl</groupId>
            <artifactId>check-spring-boot-starter</artifactId>
            <version>1.1-SNAPSHOT</version>
        </dependency>

在引用项目中的pom文件配置groupId，artifactId，version即可。下文为start中的pom。与上文配置需要对应。

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>cn.baocl</groupId>
    <artifactId>check-spring-boot-starter</artifactId>
    <version>1.1-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.2.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>
        <!-- Druid 数据连接池依赖 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.17</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <version>2.2.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
            <version>8.0.16</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
            <version>2.2.1.RELEASE</version>
        </dependency>
    </dependencies>

</project>
        

9.使用

然后就可以使用了，本文实现的为主项目定义一个从数据源。所以在主项目中就可以使用上文定义的数据源啦。

10.项目结构

​

 一、StartUML介绍

        StarUML是一款开放源码的UML开发工具，是由韩国公司主导开发出来的产品，可以直接到StarUML网站下载。可以用来创建UML类图，是软件工程建模的基本工具

 二、StartUML下载及注册

相信大家都在找startUML的注册方法，下面小编为大家提供简单的注册方法。

1.进入官网StarUML下载3.1.0版本的startUML；

​ 

2.替换starUML安装路径下resourse中的app.asar即可；

​

附录：app.asar的分享链接: https://pan.baidu.com/s/1NzGoh9br-iXsnvavvOLgZQ

提取码: tqp4

 三、StartUML使用说明

这个使用比较简单，我们不用建立工程，直接选择你想要绘画的类图的种类即可。

如：绘制用例图

亦或者你想要绘制活动图

其他的类型也是可以在StartUML上绘制的，最重要的是选对绘制类型，不然就会很难受。 

Tomcat启动报A child container failed during start问题解决

排查方案，把.xml内无关的所有注释掉，启动程序，如果成功了，就一点点代码还原+重启，直至找到致命的那行代码！（比如web.xml、pom.xml）

报错详情：

严重: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/MyMaven]]
	at java.util.concurrent.FutureTask.report(Unknown Source)
	at java.util.concurrent.FutureTask.get(Unknown Source)
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:931)
	at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:850)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1412)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1402)
	at java.util.concurrent.FutureTask.run(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/MyMaven]]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167)
	... 6 more
Caused by: java.lang.IllegalArgumentException: The session tracking mode [SSL] requested for context [/MyMaven] is not supported by that context
	at org.apache.catalina.core.ApplicationContext.setSessionTrackingModes(ApplicationContext.java:1069)
	at org.apache.catalina.core.ApplicationContextFacade.setSessionTrackingModes(ApplicationContextFacade.java:626)
	at org.apache.catalina.startup.ContextConfig.configureContext(ContextConfig.java:1400)
	at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1156)
	at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:769)
	at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:299)
	at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:94)
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5063)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	... 6 more

七月 30, 2020 4:43:50 下午 org.apache.catalina.core.ContainerBase startInternal
严重: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
	at java.util.concurrent.FutureTask.report(Unknown Source)
	at java.util.concurrent.FutureTask.get(Unknown Source)
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:931)
	at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:258)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.core.StandardService.startInternal(StandardService.java:422)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:770)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.startup.Catalina.start(Catalina.java:688)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:353)
	at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:493)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1412)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1402)
	at java.util.concurrent.FutureTask.run(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:942)
	at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:850)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	... 6 more
Caused by: java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/MyMaven]]
	at java.util.concurrent.FutureTask.report(Unknown Source)
	at java.util.concurrent.FutureTask.get(Unknown Source)
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:931)
	... 8 more
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/MyMaven]]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167)
	... 6 more
Caused by: java.lang.IllegalArgumentException: The session tracking mode [SSL] requested for context [/MyMaven] is not supported by that context
	at org.apache.catalina.core.ApplicationContext.setSessionTrackingModes(ApplicationContext.java:1069)
	at org.apache.catalina.core.ApplicationContextFacade.setSessionTrackingModes(ApplicationContextFacade.java:626)
	at org.apache.catalina.startup.ContextConfig.configureContext(ContextConfig.java:1400)
	at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1156)
	at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:769)
	at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:299)
	at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:94)
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5063)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	... 6 more

没有任何有用的提示，就是启动失败，弹框报错。
问了度娘，记下一些步骤：

1、servlet-api包冲突

• 出现这个问题的原因是导入了servlet-api包，与tomcat7的依赖包servlet-api冲突
• 检查pom.xml是否导入servlet-api
• 加上<scope>provided</scope>之后再次运行，成功启动

2、找到问题了

• 提示很明显了，[SSL] requested表示你的xml有地方配置了SSL请求方式。
• 多看报错提示。
• 排查方案，把.xml内无关的所有注释掉，启动程序，如果成功了，就一点点代码还原+重启，直至找到致命的那行代码！

排查方案，把.xml内无关的所有注释掉，启动程序，如果成功了，就一点点代码还原+重启，直至找到致命的那行代码！（比如web.xml、pom.xml）