RaigorJiang commented on issue #15712:
URL:
https://github.com/apache/shardingsphere/issues/15712#issuecomment-1073984494
Hi @Swastyy
Here are some instructions and sample snippets:
1. Startup class
Reference to:
`org.apache.shardingsphere.example.sharding.raw.jdbc.ShardingRawJavaConfigurationExample`
2. DataSourceFactory
Reference to:
`org.apache.shardingsphere.example.sharding.raw.jdbc.factory.DataSourceFactory`
3. DataSourceConfiguration
Reference to:
`org.apache.shardingsphere.example.sharding.raw.jdbc.config.ShardingDatabasesConfigurationPrecise`
Application:
- In ShardingDatabasesConfigurationPrecise:
```java
private ShardingRuleConfiguration createShardingRuleConfiguration() {
ShardingRuleConfiguration result = new ShardingRuleConfiguration();
...
result.setDefaultDatabaseShardingStrategy(new
StandardShardingStrategyConfiguration("user_id", "inline"));
Properties props = new Properties();
props.setProperty("algorithm-expression", "demo_ds_${user_id % 2}");
result.getShardingAlgorithms().put("inline", new
ShardingSphereAlgorithmConfiguration("INLINE", props));
...
return result;
}
```
The `new ShardingSphereAlgorithmConfiguration` specifies the use of the
`INLINE` algorithm, and passes in a property containing "algorithm-expression"
as a parameter. In the algorithm map, the key is also `inline`.
At the same time, a `StandardShardingStrategyConfiguration` is created in
`defaultDatabaseShardingStrategy`, and `inline` (here is the key of map) is
applied.
- Custom Algorithm:
Take
`org.apache.shardingsphere.example.extension.classbased.sharding.raw.jdbc.fixture.ClassBasedStandardShardingAlgorithmFixture`
as an example, it accepts a parameter "sharding-count" to calculate sharding
count:
```java
@Override
public String doSharding(final Collection<String> availableTargetNames,
final PreciseShardingValue<Integer> shardingValue) {
for (String each : availableTargetNames) {
if (each.endsWith(String.valueOf(shardingValue.getValue() %
shardingCount))) {
return each;
}
}
return null;
}
```
In the new `ShardingDatabasesConfigurationPrecise`, we can define:
````java
private ShardingRuleConfiguration createShardingRuleConfiguration() {
ShardingRuleConfiguration result = new ShardingRuleConfiguration();
...
result.setDefaultDatabaseShardingStrategy(new
StandardShardingStrategyConfiguration("user_id", "custom"));
Properties props = new Properties();
props.setProperty("strategy", "standard");
props.setProperty("algorithmClassName",
"org.apache.shardingsphere.example.extension.classbased.sharding.raw.jdbc.fixture.ClassBasedStandardShardingAlgorithmFixture");
props.setProperty("sharding-count", "4");
result.getShardingAlgorithms().put("custom", new
ShardingSphereAlgorithmConfiguration("CLASS_BASED", props));
...
return result;
}
````
illustrate:
- Because `ClassBasedStandardShardingAlgorithmFixture` implements
`StandardShardingAlgorithm`, the strategy in props is `standard`;
- `algorithmClassName` is used to specify the custom algorithm to use;
- `sharding-count` is a parameter required by the algorithm.
The other parts are basically the same as the `sharding-raw-jdbc-example`.
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