SpringBoot配置走数据库（自定义配置源）

SpringBoot配置走数据库（自定义配置源）

有时候我们想更改一些配置而又不像重新修改yml或者properties文件重新打包，除了springcloud的config之外，我们可以把配置写在数据库中通过 @Value("${xxx.xxx}")的方式去使用。

Mysql定义配置表格

DROP TABLE IF EXISTS `tb_system_properties`;
CREATE TABLE `tb_system_properties`  (
  `k` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NOT NULL COMMENT '键',
  `v` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NULL DEFAULT NULL COMMENT '值',
  `remark` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NOT NULL COMMENT '备注',
  PRIMARY KEY (`k`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_bin COMMENT = '系统属性表' ROW_FORMAT = Dynamic;

自定义配置源

import org.springframework.boot.SpringApplication;
import org.springframework.boot.env.EnvironmentPostProcessor;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.core.Ordered;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.MapPropertySource;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.HashMap;
import java.util.Map;

/**
 * @author oujiangping
 */
public class DbPropertiesPostProcessor implements EnvironmentPostProcessor {
    /**
     * Name of the custom property source added by this post processor class
     */
    private static final String PROPERTY_SOURCE_NAME = "databaseProperties";

    /**
     * Adds Spring Environment custom logic. This custom logic fetch properties from database and setting highest precedence
     */
    @Override
    public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
        System.out.println("DbPropertiesPostProcessor.postProcessEnvironment");
        Map<String, Object> propertySource = new HashMap<>();

        try {

            // Build manually datasource to ServiceConfig
            DataSource ds = DataSourceBuilder
                    .create()
                    .username(environment.getProperty("spring.datasource.username"))
                    .password(environment.getProperty("spring.datasource.password"))
                    .url(environment.getProperty("spring.datasource.url"))
                    .driverClassName("com.mysql.jdbc.Driver")
                    .build();

            // Fetch all properties

            Connection connection = ds.getConnection();

            System.out.println("ReadDbPropertiesPostProcessor configuracion from database");

            PreparedStatement preparedStatement = connection.prepareStatement("SELECT * FROM tb_system_properties");


            ResultSet rs = preparedStatement.executeQuery();

            // Populate all properties into the property source
            while (rs.next()) {
                propertySource.put(rs.getString("k"), rs.getString("v"));
            }

            rs.close();
            preparedStatement.clearParameters();


            preparedStatement.close();
            connection.close();

            // Create a custom property source with the highest precedence and add it to Spring Environment
            environment.getPropertySources().addFirst(new MapPropertySource(PROPERTY_SOURCE_NAME, propertySource));

        } catch (Throwable e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }
}

指定EnvironmentPostProcessor

在resources目录下添加文件META-INF/spring.factories，内容如下：

org.springframework.boot.env.EnvironmentPostProcessor=xxx.xxx.DbPropertiesPostProcessor

使用

1. 数据库添加配置如：k = test.abc, v= hello world
2. 在使用的地方使用@Value("${test.abc}")既可以使用

大功告成！！！