[springboot 2019-10-23] 自定义springboot自动配置

1.创建springboot 3个关键类

1.1 属性读取类：用于从配置文件中读取配置信息

package com.shijt.springbootdemo.jdbc;

import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "mysql.jdbc")
public class JDBCRead {
    private String driver;
    private String url;
    private String username;
    private String password;

    public String getDriver() {
        return driver;
    }

    public void setDriver(String driver) {
        this.driver = driver;
    }

    public String getUrl() {
        return url;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

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

1.2 核心事件类

package com.shijt.springbootdemo.jdbc;

import java.sql.*;

public class JDBCUtils {
    private String driver;
    private String url;
    private String username;
    private String password;

    public int testJdbc(){

        Connection con = null;
        try{
            //加载MySql的驱动类
            Class.forName("com.mysql.jdbc.Driver") ;
            con = DriverManager.getConnection(url , username , password ) ;
　　　　　　　//仅做测试，直接写死了sql
            String sql="INSERT INTO `smbms_user` (`id`, `userCode`, `userName`) VALUES ('001', '001', 'zhangsan')";
            PreparedStatement pstmt = con.prepareStatement(sql) ;
            int rows = pstmt.executeUpdate() ;
            pstmt.close();
            return rows;
        }catch(ClassNotFoundException e){
            System.out.println("找不到驱动程序类 ，加载驱动失败！");
            e.printStackTrace() ;
        }catch(SQLException se){
            System.out.println("数据库连接失败！");
            se.printStackTrace() ;
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if (con != null){
                try {
                    con.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        return 0;
    }

    public String getDriver() {
        return driver;
    }

    public void setDriver(String driver) {
        this.driver = driver;
    }

    public String getUrl() {
        return url;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

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

1.3 整合类：把属性读取类中的属性赋值给核心事件类

package com.shijt.springbootdemo.jdbc;

import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.annotation.Resource;

@Configuration
@EnableConfigurationProperties({JDBCRead.class})
@ConditionalOnClass({JDBCUtils.class })
@ConditionalOnProperty(prefix="mysql.jdbc",value = "enabled",matchIfMissing = true)
public class JDBCAutoConfigration {
    @Resource
    private JDBCRead jdbcRead;

    @Bean
    @ConditionalOnMissingBean({JDBCUtils.class})
    public JDBCUtils getJDBCUtils(){
        //确定方法执行的时间（在springboot启动时，而不是调用JDBCUtils时）
        System.out.println("-----step into JDBCAutoConfigration getJDBCUtils-----");
        JDBCUtils jdbcUtils=new JDBCUtils();
        jdbcUtils.setDriver(jdbcRead.getDriver());
        jdbcUtils.setUrl(jdbcRead.getUrl());
        jdbcUtils.setUsername(jdbcRead.getUsername());
        jdbcUtils.setPassword(jdbcRead.getPassword());
        return jdbcUtils;
    }
}

2.在resources目录下META-INF文件夹，创建spring.factories文件

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.shijt.springbootdemo.jdbc.JDBCAutoConfigration

把写好的整合类加入到自动配置中

3.编写Controller类，调用JDBCUtils

package com.shijt.springbootdemo.controller;

import com.shijt.springbootdemo.jdbc.JDBCUtils;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.annotation.Resource;

@Controller
public class UserController {
    @Resource
    private JDBCUtils jdbcUtils;

    @RequestMapping("/testJdbc")
    @ResponseBody
    public int testJdbc(){
        return jdbcUtils.testJdbc();
    }

}

在appliaction.yml中配置数据库连接信息

mysql:
  jdbc:
    driver: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/smbms?useUnicode=true&characterEncoding=utf-8
    username: root
    password: 123456

4.启动springboot,测试