[GitHub] [shardingsphere] haoqg edited a comment on issue #8309: how to congurate self implement sharding algorithm？

[GitBox <gi...@apache.org>]

haoqg edited a comment on issue #8309:
URL: https://github.com/apache/shardingsphere/issues/8309#issuecomment-733615552


   5.0 是用的SPI机制，假如需要使用自定义分库或者分表策略的话，以官方的mod为例子，我们需要这么干，首先
   在项目里的resources 目录下新建一个文件夹  META-INF/services，文件夹里新建一个文件org.apache.shardingsphere.sharding.spi.ShardingAlgorithm
   ![image](https://user-images.githubusercontent.com/9582571/100214534-fb971500-2f4a-11eb-9a29-64990c165bed.png)
   在此文件里把自己的类加上
   比如，我这里新建一个类，
   
   
   `public final class BatchIdShardingAlgorithm implements StandardShardingAlgorithm<Comparable<?>>, ShardingAutoTableAlgorithm {
       private static final String SHARDING_COUNT_KEY = "sharding-count";
       private Properties props = new Properties();
       private int shardingCount;
   
       public BatchIdShardingAlgorithm() {
       }
   
       @Override
       public void init() {
           this.shardingCount = this.getShardingCount();
       }
   
       private int getShardingCount() {
           return 0;
       }
   
       @Override
       public String doSharding(Collection<String> availableTargetNames, PreciseShardingValue<Comparable<?>> shardingValue) {
   
        //todo 自己的分表逻辑
           return "0";
       }
   
       @Override
       public Collection<String> doSharding(Collection<String> availableTargetNames, RangeShardingValue<Comparable<?>> shardingValue) {
           return this.isContainAllTargets(shardingValue) ? availableTargetNames : this.getAvailableTargetNames(availableTargetNames, shardingValue);
       }
   
       private boolean isContainAllTargets(RangeShardingValue<Comparable<?>> shardingValue) {
           return !shardingValue.getValueRange().hasUpperBound() || shardingValue.getValueRange().hasLowerBound() && this.getLongValue(shardingValue.getValueRange().upperEndpoint()) - this.getLongValue(shardingValue.getValueRange().lowerEndpoint()) >= (long)(this.shardingCount - 1);
       }
   
       private Collection<String> getAvailableTargetNames(Collection<String> availableTargetNames, RangeShardingValue<Comparable<?>> shardingValue) {
           Collection<String> result = new LinkedHashSet(availableTargetNames.size());
   
           for(long i = this.getLongValue(shardingValue.getValueRange().lowerEndpoint()); i <= this.getLongValue(shardingValue.getValueRange().upperEndpoint()); ++i) {
               Iterator var6 = availableTargetNames.iterator();
   
               while(var6.hasNext()) {
                   String each = (String)var6.next();
                   if (each.endsWith(String.valueOf(i % (long)this.shardingCount))) {
                       result.add(each);
                   }
               }
           }
   
           return result;
       }
   
       private long getLongValue(Comparable<?> value) {
           return Long.parseLong(value.toString());
       }
   
       @Override
       public int getAutoTablesAmount() {
           return this.shardingCount;
       }
   
       @Override
       public String getType() {
           return "BATCH-ID";
       }
   
       @Override
       public Collection<String> getAllPropertyKeys() {
           return Collections.singletonList("sharding-count");
       }
   
       @Override
       @Generated
       public Properties getProps() {
           return this.props;
       }
   
       @Override
       @Generated
       public void setProps(Properties props) {
           this.props = props;
       }
   
       @Generated
       public void setShardingCount(int shardingCount) {
           this.shardingCount = shardingCount;
       }
   }`
   
   然后就可以使用自定义的策略了
   
   Properties tableShardingAlgorithmrProps = new Properties();
           shardingRuleConfig.getShardingAlgorithms().put("tableShardingAlgorithm", new ShardingSphereAlgorithmConfiguration("BATCH-ID", tableShardingAlgorithmrProps));
   
   大概就是这么个机制，
   其实源码里就是这么干的，有图为证
   ![image](https://user-images.githubusercontent.com/9582571/100214851-516bbd00-2f4b-11eb-9389-c25b770b6a15.png)
   


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