shardingjdbc4.x初始化数据源过程

前言

看过好几遍了老是忘记，idea点击配置时总是跳转到DataSourceUtil中引起误解。所以我这次要把他记录下来。

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使用shardingjdbc4.x配置数据源时，一般我们是这个配置的。那他背后是如何将数据源创建出来的呢，下面请看源码。

spring.shardingsphere.datasource.names=ds0,ds1

spring.shardingsphere.datasource.ds0.type=com.zaxxer.hikari.HikariDataSource
spring.shardingsphere.datasource.ds0.driver-class-name=software.aws.rds.jdbc.mysql.Driver
spring.shardingsphere.datasource.ds0.jdbc-url=jdbc:mysql:127.0.0.1:3306/xxx?useUnicode=true&characterEncoding=utf-8&transformedBitIsBoolean=true&allowMultiQueries=true&useSSL=false
spring.shardingsphere.datasource.ds0.username=username
spring.shardingsphere.datasource.ds0.password=password

spring.shardingsphere.datasource.ds1.type=com.zaxxer.hikari.HikariDataSource
spring.shardingsphere.datasource.ds1.driver-class-name=software.aws.rds.jdbc.mysql.Driver
spring.shardingsphere.datasource.ds1.jdbc-url=jdbc:mysql:127.0.0.1:3306/xxx?useUnicode=true&characterEncoding=utf-8&transformedBitIsBoolean=true&allowMultiQueries=true&useSSL=false
spring.shardingsphere.datasource.ds1.username=username
spring.shardingsphere.datasource.ds1.password=password

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这里我们使用Hikari连接池初始化了两个名称为ds0,ds1的数据源。下面解释下他背后是怎么配置数据源的

首先在：org.apache.shardingsphere.shardingjdbc.spring.boot.SpringBootConfiguration 类中有下面这样一段代码

他会从环境中查找 spring.shardingsphere.datasource.names前缀的配置，也就是我们上面的配置的两个数据源名字，逗号分隔
然后依次将每个数据源名称前面拼接上 spring.shardingsphere.datasource.前缀开始查找配置，并使用 DataSourceUtil工具类将数据源反射创建出来。

@Override
public final void setEnvironment(final Environment environment) {
    String prefix = "spring.shardingsphere.datasource.";
    for (String each : getDataSourceNames(environment, prefix)) {
        try {
            dataSourceMap.put(each, getDataSource(environment, prefix, each));
        } catch (final ReflectiveOperationException ex) {
            throw new ShardingSphereException("Can't find datasource type!", ex);
        } catch (final NamingException namingEx) {
            throw new ShardingSphereException("Can't find JNDI datasource!", namingEx);
        }
    }
}

private List<String> getDataSourceNames(final Environment environment, final String prefix) {
    StandardEnvironment standardEnv = (StandardEnvironment) environment;
    standardEnv.setIgnoreUnresolvableNestedPlaceholders(true);
    return null == standardEnv.getProperty(prefix + "name")
            ? new InlineExpressionParser(standardEnv.getProperty(prefix + "names")).splitAndEvaluate() : Collections.singletonList(standardEnv.getProperty(prefix + "name"));
}
  
@SuppressWarnings("unchecked")
private DataSource getDataSource(final Environment environment, final String prefix, final String dataSourceName) throws ReflectiveOperationException, NamingException {
    Map<String, Object> dataSourceProps = PropertyUtil.handle(environment, prefix + dataSourceName.trim(), Map.class);
    Preconditions.checkState(!dataSourceProps.isEmpty(), "Wrong datasource properties!");
    if (dataSourceProps.containsKey(jndiName)) {
        return getJndiDataSource(dataSourceProps.get(jndiName).toString());
    }
    DataSource result = DataSourceUtil.getDataSource(dataSourceProps.get("type").toString(), dataSourceProps);
    DataSourcePropertiesSetterHolder.getDataSourcePropertiesSetterByType(dataSourceProps.get("type").toString()).ifPresent(
        dataSourcePropertiesSetter -> dataSourcePropertiesSetter.propertiesSet(environment, prefix, dataSourceName, result));
    return result;
}

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DataSourceUtil根据指定的dataSourceClassName反射创建数据源，在赋值属性时，会根据属性名查找set方法，并对一些基本类型做转换

@NoArgsConstructor(access = AccessLevel.PRIVATE)
public final class DataSourceUtil {
  
    private static final String SET_METHOD_PREFIX = "set";
  
    private static final Collection<Class<?>> GENERAL_CLASS_TYPE;
  
    static {
        GENERAL_CLASS_TYPE = Sets.newHashSet(boolean.class, Boolean.class, int.class, Integer.class, long.class, Long.class, String.class, Collection.class);
    }
  
    /**
     * Get data source.
     *
     * @param dataSourceClassName data source class name
     * @param dataSourceProperties data source properties
     * @return data source instance
     * @throws ReflectiveOperationException reflective operation exception
     */
    public static DataSource getDataSource(final String dataSourceClassName, final Map<String, Object> dataSourceProperties) throws ReflectiveOperationException {
        DataSource result = (DataSource) Class.forName(dataSourceClassName).newInstance();
        for (Entry<String, Object> entry : dataSourceProperties.entrySet()) {
            callSetterMethod(result, getSetterMethodName(entry.getKey()), null == entry.getValue() ? null : entry.getValue().toString());
        }
        return result;
    }
  
    private static String getSetterMethodName(final String propertyName) {
        if (propertyName.contains("-")) {
            return CaseFormat.LOWER_HYPHEN.to(CaseFormat.LOWER_CAMEL, SET_METHOD_PREFIX + "-" + propertyName);
        }
        return SET_METHOD_PREFIX + String.valueOf(propertyName.charAt(0)).toUpperCase() + propertyName.substring(1);
    }
  
    private static void callSetterMethod(final DataSource dataSource, final String methodName, final String setterValue) {
        for (Class<?> each : GENERAL_CLASS_TYPE) {
            try {
                Method method = dataSource.getClass().getMethod(methodName, each);
                if (boolean.class == each || Boolean.class == each) {
                    method.invoke(dataSource, Boolean.valueOf(setterValue));
                } else if (int.class == each || Integer.class == each) {
                    method.invoke(dataSource, Integer.parseInt(setterValue));
                } else if (long.class == each || Long.class == each) {
                    method.invoke(dataSource, Long.parseLong(setterValue));
                } else if (Collection.class == each) {
                    method.invoke(dataSource, Arrays.asList(setterValue.split(",")));
                } else {
                    method.invoke(dataSource, setterValue);
                }
                return;
            } catch (final ReflectiveOperationException ignored) {
            }
        }
    }
}