tkmybatis 中 主键采用UUID时主键回写的两种解决方案

最近用tkmybatis插件做项目时，发现在事务中有些新插入的数据需要被用到主键，主键不能回写，特意查了下原先作者的文档和博客，发现没有uuid的回写实现，只能自己写个用下，现发出来分享下，愿以后的小伙伴都能有分享精神。

主键采用UUID时主键回写的两种解决方案，都是才用mybatis插件形式实现。

1）线程局部变量实现方式

@Intercepts({
	@Signature(type=StatementHandler.class, method="update", args={ Statement.class }),
	@Signature(type=Executor.class, method="update", args={MappedStatement.class, Object.class})
})
public class BackWriteInterceptor implements Interceptor {

	private static final String DEFAULT_PRIMARY_KEY_NAME = "uid";

	private static final ThreadLocal<Boolean> LOCAL_BACK_WRITE = new ThreadLocal<Boolean>();

	private String primaryKeyPropertyName = DEFAULT_PRIMARY_KEY_NAME;

	@Override
	public Object intercept(Invocation invocation) throws Throwable {
		Object target = invocation.getTarget();
		if (target instanceof StatementHandler) {
			return doInterceptStatementHandler(invocation, (StatementHandler) target);
		} else if (target instanceof Executor) {
			Object[] args = invocation.getArgs();
			return doInterceptExecutor(invocation, (MappedStatement) args[0], args[1]);
		}
		return invocation.proceed();
	}

	private Object doInterceptExecutor(Invocation invocation, MappedStatement ms, Object argument) 
			throws Throwable {
		if (ms.getSqlCommandType().equals(SqlCommandType.INSERT) 
				&& argument instanceof PO) {
			LOCAL_BACK_WRITE.set(true);
		}
		try {
			return invocation.proceed();
		} catch (Exception e) {
			throw e;
		} finally {
			LOCAL_BACK_WRITE.remove();
		}
	}

	private Object doInterceptStatementHandler(Invocation invocation, StatementHandler statementHandler)
			throws Throwable {
		Boolean localBackWrite = LOCAL_BACK_WRITE.get();
		BoundSql boundSql = statementHandler.getBoundSql();
		Object parameterObject = boundSql.getParameterObject();
		if (localBackWrite != null && localBackWrite && parameterObject instanceof PO) {
			String uid = (String) boundSql.getAdditionalParameter(this.primaryKeyPropertyName + "_bind");
			((PO) parameterObject).setUid(uid);
			LOCAL_BACK_WRITE.set(false);
		}
		return invocation.proceed();
	}

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

	@Override
	public void setProperties(Properties properties) {
		if (properties.containsKey("primaryKeyPropertyName")) {
			primaryKeyPropertyName = (String) properties.get("primaryKeyPropertyName");
		}
	}

}

2）自定义KeyGenerator

@Intercepts(@Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class}))
public class BackWriteInterceptor implements Interceptor {

	@Override
	public Object intercept(Invocation invocation) throws Throwable {
		Object[] args = invocation.getArgs();
		MappedStatement ms = (MappedStatement) args[0];
		Object argument = args[1];
		if(ms.getSqlCommandType().equals(SqlCommandType.INSERT) && 
				NoKeyGenerator.class.equals(ms.getKeyGenerator().getClass()) &&
				PO.class.isAssignableFrom(argument.getClass())) {
			MetaObject metaObject = SystemMetaObject.forObject(ms);
			metaObject.setValue("keyGenerator", BackWriteKeyGenerator.instance());
		}
		return invocation.proceed();
	}

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

	@Override
	public void setProperties(Properties properties) {
		
	}

}

public class BackWriteKeyGenerator implements KeyGenerator {

	private static final BackWriteKeyGenerator instance = new BackWriteKeyGenerator();

	public static BackWriteKeyGenerator instance() {
		return instance;
	}

	@Override
	public void processBefore(Executor executor, MappedStatement ms, Statement stmt, Object parameter) {
		if (parameter instanceof PO) {
			((PO) parameter).setUid(UUID.randomUUID().toString().replaceAll("-", ""));
		}
	}

	@Override
	public void processAfter(Executor executor, MappedStatement ms, Statement stmt, Object parameter) {

	}

}

两种方案各有优劣，有兴趣的可以自己研究下。