Fixes #2629

[sunbufu]

Changes proposed in this pull request:

• throw ShardingException when execute RoutingEngine.newInstance() with null ShardingRule
• avoid NPE when execute ShardingDataSourceNames.getDefaultDataSourceName() with null shardingRuleConfig

Hello, this is my first PR for shardingsphere. so If I do something wrong, please let me know. Thank U.

[coveralls]

Pull Request Test Coverage Report for Build 8742

• 84 of 243 (34.57%) changed or added relevant lines in 29 files are covered.
• 2 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.2%) to 61.523%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/entry/EncryptSQLParseEntry.java	0	1	0.0%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/entry/MasterSlaveSQLParseEntry.java	0	1	0.0%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/entry/ShardingSQLParseEntry.java	0	1	0.0%
sharding-core/sharding-core-parse/sharding-core-parse-mysql/src/main/java/org/apache/shardingsphere/core/parse/filler/dal/MySQLShowLikeFiller.java	0	1	0.0%
sharding-core/sharding-core-rewrite/src/main/java/org/apache/shardingsphere/core/rewrite/builder/BaseParameterBuilder.java	0	1	0.0%
sharding-jdbc/sharding-jdbc-core/src/main/java/org/apache/shardingsphere/shardingjdbc/jdbc/core/datasource/EncryptDataSource.java	0	1	0.0%
sharding-proxy/sharding-proxy-frontend/sharding-proxy-frontend-mysql/src/main/java/org/apache/shardingsphere/shardingproxy/frontend/mysql/command/query/binary/prepare/MySQLComStmtPrepareExecutor.java	0	1	0.0%
sharding-proxy/sharding-proxy-frontend/sharding-proxy-frontend-postgresql/src/main/java/org/apache/shardingsphere/shardingproxy/frontend/postgresql/command/query/binary/parse/PostgreSQLComParseExecutor.java	0	1	0.0%
sharding-core/sharding-core-merge/src/main/java/org/apache/shardingsphere/core/merge/dql/DQLMergeEngine.java	9	11	81.82%
sharding-proxy/sharding-proxy-backend/src/main/java/org/apache/shardingsphere/shardingproxy/backend/schema/EncryptSchema.java	0	2	0.0%

Files with Coverage Reduction	New Missed Lines	%
sharding-core/sharding-core-optimize/src/main/java/org/apache/shardingsphere/core/optimize/statement/sharding/dml/select/Pagination.java	1	0.0%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/SQLParseEngine.java	1	0.0%

Totals
Change from base Build 8713:	0.2%
Covered Lines:	8444
Relevant Lines:	13725

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💛 - Coveralls

[sunbufu]

#2629

[tristaZero]

Hi, thanks for your pr.
In your pr, you said that if there is no shardingRule, RoutingEngine.newInstance() and RoutingEngine.newInstance() will throw NPE. But when will the shardingRule be null? Because if you want to sharding tables, shardingRule is necessary, otherwise you can not start up.
Can u give me some scenerios?

[sunbufu]

Hi, thanks for your pr.
In your pr, you said that if there is no shardingRule, RoutingEngine.newInstance() and RoutingEngine.newInstance() will throw NPE. But when will the shardingRule be null? Because if you want to sharding tables, shardingRule is necessary, otherwise you can not start up.
Can u give me some scenerios?

Thank you for reply. I agree with you, and In my view, I think RoutingEngine.newInstance() should throw ShardingException replace NPE, when ShardingRule is empty (include null). You can find this code on RoutingEngineFactory in line 68 to 70.
And, I think ShardingDataSourceNames is same with RoutingEngine. This code in lines 45 to 47 on ShardingDataSourceNames of my PR.

[tristaZero]

Hi, Considering user will create ShardingRule to create ShardingDataSource, i think it is better to judge whether null == shardingRuleConfig, but do you think it is better to add this judgement in ShardingRule.java?

public ShardingRule(final ShardingRuleConfiguration shardingRuleConfig, final Collection<String> dataSourceNames) {
        // Here just checking dataSourceNames, maybe we can add checking shardingRuleConfig?
        Preconditions.checkArgument(!.isEmpty(), "Data sources cannot be empty.");
        this.shardingRuleConfig = shardingRuleConfig;
       // If we add shardingRuleConfig checking ahead, there is no chance to enter into it, if shardingRuleConfig is null.
        shardingDataSourceNames = new ShardingDataSourceNames(shardingRuleConfig, dataSourceNames);

Once ShardingRule, i.e, ShardingDataSource is created, it is impossible that shardingRule will be null in RoutingEngineFactory. What do you think?

[sunbufu]

You are right, ShardingRule is meaningless with a null ShardingRuleConfig. So, we need a judge in ShardingRule's constructor. and I notice there may throw a NPE in ShardingRule.createEncryptRule() when shardingRuleConfig is null.
There is a question. Should I throw a ShardingException or IllegalArgumentException on this case? If we choose ShardingException, I need modify dataSourceNames's judge too.

[sunbufu]

Confuse the commit log by rebase, so I send a new and close this.