mybatis利用插件实现分表

yuzuodeyunwcj

2019-07-01

如标题，这次的分表规则比较？？，部分用户相关表按产品维度划分，例如:user_1,user_2（1，2是产品id，新加一个产品就要新增一整套表...）研究了一波sharing-jdbc(后面改成了sharding-sphere)不太合适，也有种杀鸡牛刀的感觉。
不想手写SQL太麻烦，后面说不好表要改动，虽然有生成工具(不灵活)，所以选择了Mybatis-plus这个兄弟，借鉴他的分页等各种插件决定自己实现一个分表插件，把需要分表的表在配置中维护，利用jsqlparser解析sql重写sql语句，废话不多说上代码

/**

分表插件
@author chonglou
@date 2019/2/2117:04

*/
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class ShardInterceptor implements Interceptor, ShardAgent {

private final ShardProperties shardProperties;

public ShardInterceptor(ShardProperties shardProperties) {
    this.shardProperties = shardProperties;
}

public static final CCJSqlParserManager parser = new CCJSqlParserManager();

@Override
public Object intercept(Invocation invocation) throws Throwable {
    StatementHandler statementHandler = (StatementHandler) realTarget(invocation.getTarget());
    MetaObject metaObject = SystemMetaObject.forObject(statementHandler);
    MappedStatement mappedStatement = (MappedStatement) metaObject.getValue("delegate.mappedStatement");
    if (!shardProperties.isException(mappedStatement.getId())) {
        if (SqlCommandType.INSERT.equals(mappedStatement.getSqlCommandType())
                || SqlCommandType.SELECT.equals(mappedStatement.getSqlCommandType())
                || SqlCommandType.UPDATE.equals(mappedStatement.getSqlCommandType())
                || SqlCommandType.DELETE.equals(mappedStatement.getSqlCommandType())) {

            String sql = statementHandler.getBoundSql().getSql();
            Statement statement = parser.parse(new StringReader(sql));
            if (statement instanceof Select) {
                Select select = (Select) statement;
                TableNameModifier modifier = new TableNameModifier(this);
                select.getSelectBody().accept(modifier);
            } else if (statement instanceof Update) {
                Update update = (Update) statement;
                List<Table> list = update.getTables();
                for (Table t : list) {
                    parserTable(t, true);
                }
            } else if (statement instanceof Delete) {
                Delete delete = (Delete) statement;
                parserTable(delete.getTable(), true);
                List<Table> list = delete.getTables();
                for (Table t : list) {
                    parserTable(t, true);
                }
            } else if (statement instanceof Insert) {
                Insert insert = (Insert) statement;
                parserTable(insert.getTable(), false);
            }
            StatementDeParser deParser = new StatementDeParser(new StringBuilder());
            statement.accept(deParser);
            sql = deParser.getBuffer().toString();
            ReflectionUtils.setFieldValue(statementHandler.getBoundSql(), "sql", sql);
        }
    }
    return invocation.proceed();
}

private Object realTarget(Object target) {
    if (Proxy.isProxyClass(target.getClass())) {
        MetaObject metaObject = SystemMetaObject.forObject(target);
        return realTarget(metaObject.getValue("h.target"));
    } else {
        return target;
    }
}

/**
 * 覆盖表名设置别名
 *
 * @param table
 * @return
 */
private Table parserTable(Table table, boolean alias) {
    if (null != table) {
        if (alias) {
            table.setAlias(new Alias(table.getName()));
        }
        table.setName(getTargetTableName(table.getName()));
    }
    return table;
}

@Override
public Object plugin(Object target) {
    if (target instanceof StatementHandler) {
        return Plugin.wrap(target, this);
    }
    return target;
}

@Override
public void setProperties(Properties properties) {
}

@Override
public String getTargetTableName(String tableName) {
    if (shardProperties.isAgentTable(tableName)) {
        return ShardUtil.getTargetTableName(tableName);
    }
    return tableName;
}

}

/**

@author chonglou
@date 2019/2/2218:24

*/
public interface ShardAgent {

String getTargetTableName(String name);

}

/**
*工具

@author chonglou
@date 2019/2/2514:11

*/
public class ShardUtil {

private final static String KEY_GENERATOR = "keyGenerator";

public static void setKeyGenerator(Object keyGenerator) {
    HttpServletRequest request = SpringContextHolder.getRequest();
    request.setAttribute(KEY_GENERATOR, keyGenerator);
}

public static String getTargetTableName(String tableName) {
    HttpServletRequest request = SpringContextHolder.getRequest();
    Object productId = request.getAttribute(KEY_GENERATOR);
    if (null == productId) {
        throw new RuntimeException("keyGenerator is null.");
    }
    return tableName.concat("_").concat(productId.toString());
}

}

/**

Spring的ApplicationContext的持有者,可以用静态方法的方式获取spring容器中的bean,
Request 以及 Session

@author chonglou

*/
@Component
public class SpringContextHolder implements ApplicationContextAware {

private static ApplicationContext applicationContext;

@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    SpringContextHolder.applicationContext = applicationContext;
}

public static ApplicationContext getApplicationContext() {
    assertApplicationContext();
    return applicationContext;
}

public static <T> T getBean(String beanName) {
    assertApplicationContext();
    return (T) applicationContext.getBean(beanName);
}

public static <T> T getBean(Class<T> requiredType) {
    assertApplicationContext();
    return applicationContext.getBean(requiredType);
}

private static void assertApplicationContext() {
    if (null == SpringContextHolder.applicationContext) {
        throw new RuntimeException("applicationContext属性为null,请检查是否注入了SpringContextHolder!");
    }
}

/**
 * 获取当前请求的Request对象
 *
 * @return HttpServletRequest
 */
public static HttpServletRequest getRequest() {
    ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
    return requestAttributes.getRequest();
}

/**
 * 获取当前请求的session对象
 *
 * @return HttpSession
 */
public static HttpSession getSession() {
    return getRequest().getSession();
}

}

/**

查询语句修改
@author chonglou
@date 2019/2/2211:31

*/
public class TableNameModifier extends SelectDeParser {

private ShardAgent shardAgent;

TableNameModifier(ShardAgent shardAgent) {
    super();
    this.shardAgent = shardAgent;
}

@Override
public void visit(Table tableName) {
    StringBuilder buffer = new StringBuilder();
    tableName.setName(shardAgent.getTargetTableName(tableName.getName()));
    buffer.append(tableName.getFullyQualifiedName());
    Alias alias = tableName.getAlias();
    if (alias == null) {
        alias = new Alias(tableName.getName());
    }
    buffer.append(alias);
    Pivot pivot = tableName.getPivot();
    if (pivot != null) {
        pivot.accept(this);
    }

    MySQLIndexHint indexHint = tableName.getIndexHint();
    if (indexHint != null) {
        buffer.append(indexHint);
    }

}

}
/**

@author chonglou
@date 2019/2/2215:34

*/
@ConfigurationProperties(prefix = "shard.config")
public class ShardProperties {

private List<String> exceptionMapperId;

private List<String> agentTables;

public boolean isException(String mapperId) {
    return null != exceptionMapperId && exceptionMapperId.contains(mapperId);
}

public boolean isAgentTable(String tableName) {
    return null != agentTables && agentTables.contains(tableName);
}

public List<String> getExceptionMapperId() {
    return exceptionMapperId;
}

public void setExceptionMapperId(List<String> exceptionMapperId) {
    this.exceptionMapperId = exceptionMapperId;
}

public List<String> getAgentTables() {
    return agentTables;
}

public void setAgentTables(List<String> agentTables) {
    this.agentTables = agentTables;
}

}

select update mybatis