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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
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 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.hadoop.hbase.constraint;

import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.hbase.client.Put;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * Apply a {@link Constraint} (in traditional database terminology) to a HTable. Any number of
 * {@link Constraint Constraints} can be added to the table, in any order.
 * 

* A {@link Constraint} must be added to a table before the table is loaded via * {@link Constraints#add(org.apache.hadoop.hbase.HTableDescriptor, Class[])} or * {@link Constraints#add(org.apache.hadoop.hbase.HTableDescriptor, org.apache.hadoop.hbase.util.Pair...)} * (if you want to add a configuration with the {@link Constraint}). Constraints will be run in the * order that they are added. Further, a Constraint will be configured before it is run (on load). *

* See {@link Constraints#enableConstraint(org.apache.hadoop.hbase.HTableDescriptor, Class)} and * {@link Constraints#disableConstraint(org.apache.hadoop.hbase.HTableDescriptor, Class)} for * enabling/disabling of a given {@link Constraint} after it has been added. *

* If a {@link Put} is invalid, the Constraint should throw some sort of * {@link org.apache.hadoop.hbase.constraint.ConstraintException}, indicating that the {@link Put} * has failed. When this exception is thrown, not further retries of the {@link Put} are attempted * nor are any other {@link Constraint Constraints} attempted (the {@link Put} is clearly not * valid). Therefore, there are performance implications in the order in which {@link BaseConstraint * Constraints} are specified. *

* If a {@link Constraint} fails to fail the {@link Put} via a * {@link org.apache.hadoop.hbase.constraint.ConstraintException}, but instead throws a * {@link RuntimeException}, the entire constraint processing mechanism * ({@link ConstraintProcessor}) will be unloaded from the table. This ensures that the region * server is still functional, but no more {@link Put Puts} will be checked via {@link Constraint * Constraints}. *

* Further, {@link Constraint Constraints} should probably not be used to enforce cross-table * references as it will cause tremendous write slowdowns, but it is possible. *

* NOTE: Implementing classes must have a nullary (no-args) constructor * @see BaseConstraint * @see Constraints */ @InterfaceAudience.Private public interface Constraint extends Configurable { /** * Check a {@link Put} to ensure it is valid for the table. If the {@link Put} is valid, then just * return from the method. Otherwise, throw an {@link Exception} specifying what happened. This * {@link Exception} is propagated back to the client so you can see what caused the {@link Put} * to fail. * @param p {@link Put} to check * @throws org.apache.hadoop.hbase.constraint.ConstraintException when the {@link Put} does not * match the constraint. */ void check(Put p) throws ConstraintException; }





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