qihuajun opened a new issue #3045: Sharding Proxy throw NullPointerException while querying URL: https://github.com/apache/incubator-shardingsphere/issues/3045 ## Bug Report ### Which version of ShardingSphere did you use? latest: 4.0.0-RC2 ### Which project did you use? Sharding-JDBC or Sharding-Proxy? Sharding-Proxy ### Expected behavior Executing query without exception ### Actual behavior Almost every query I performed, though I got the query result, but there's an error log record below in log file: ``` [ERROR] 20:17:38.524 [ShardingSphere-Command-5] o.a.s.s.f.c.CommandExecutorTask - Exception occur: java.lang.NullPointerException: null at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.datasource.JDBCBackendDataSource.createConnection(JDBCBackendDataSource.java:150) at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.datasource.JDBCBackendDataSource.getConnections(JDBCBackendDataSource.java:123) at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.connection.BackendConnection.getConnectionFromUnderlying(BackendConnection.java:189) at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.connection.BackendConnection.getConnectionsWithoutTransaction(BackendConnection.java:172) at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.connection.BackendConnection.getConnections(BackendConnection.java:141) at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.execute.callback.ProxyJDBCExecutePrepareCallback.getConnections(ProxyJDBCExecutePrepareCallback.java:56) at org.apache.shardingsphere.core.execute.sql.prepare.SQLExecutePrepareTemplate.getSQLExecuteGroups(SQLExecutePrepareTemplate.java:89) at org.apache.shardingsphere.core.execute.sql.prepare.SQLExecutePrepareTemplate.getSynchronizedExecuteUnitGroups(SQLExecutePrepareTemplate.java:67) at org.apache.shardingsphere.core.execute.sql.prepare.SQLExecutePrepareTemplate.getExecuteUnitGroups(SQLExecutePrepareTemplate.java:59) at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.execute.JDBCExecuteEngine.execute(JDBCExecuteEngine.java:78) at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.JDBCDatabaseCommunicationEngine.execute(JDBCDatabaseCommunicationEngine.java:95) at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.JDBCDatabaseCommunicationEngine.execute(JDBCDatabaseCommunicationEngine.java:81) at org.apache.shardingsphere.shardingproxy.backend.text.query.QueryBackendHandler.execute(QueryBackendHandler.java:54) at org.apache.shardingsphere.shardingproxy.frontend.mysql.command.query.text.query.MySQLComQueryPacketExecutor.execute(MySQLComQueryPacketExecutor.java:72) at org.apache.shardingsphere.shardingproxy.frontend.command.CommandExecutorTask.executeCommand(CommandExecutorTask.java:86) at org.apache.shardingsphere.shardingproxy.frontend.command.CommandExecutorTask.run(CommandExecutorTask.java:66) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) ``` ### Steps to reproduce the behavior, such as: SQL to execute, sharding rule configuration, when exception occur etc. Just regular config, regular sql like `show create table` or `select * from table` can prouduce the error log above. Besides this bug I reported, I also found its unfriendly for developers to use Sharding Proxy: 1. the document about Sharding Proxy is too simple, I had to read the source code to find out how to config sharding tables with self-implemented sharding algorithm 2. No detailed error message if schema config file has error configs, here is the error message I got when I start Sharding Proxy with some wrong config: ``` Exception in thread "main" Cannot create property=shardingRule for JavaBean=org.apache.shardingsphere.shardingproxy.config.yaml.YamlProxyRuleConfiguration@31304f14 in 'reader', line 1, column 1: schemaName: mbase ^ Cannot create property=tables for JavaBean=org.apache.shardingsphere.core.yaml.config.sharding.YamlShardingRuleConfiguration@6302bbb1 in 'reader', line 502, column 3: tables: ^ No single argument constructor found for class org.apache.shardingsphere.core.yaml.config.sharding.YamlTableRuleConfiguration in 'reader', line 503, column 5: brand: ^ in 'reader', line 502, column 3: tables: ^ at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:312) at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.construct(Constructor.java:189) at org.yaml.snakeyaml.constructor.Constructor$ConstructYamlObject.construct(Constructor.java:345) at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:182) at org.yaml.snakeyaml.constructor.BaseConstructor.constructDocument(BaseConstructor.java:141) at org.yaml.snakeyaml.constructor.BaseConstructor.getSingleData(BaseConstructor.java:127) at org.yaml.snakeyaml.Yaml.loadFromReader(Yaml.java:450) at org.yaml.snakeyaml.Yaml.loadAs(Yaml.java:410) at org.apache.shardingsphere.core.yaml.engine.YamlEngine.unmarshal(YamlEngine.java:59) at org.apache.shardingsphere.shardingproxy.config.ShardingConfigurationLoader.loadRuleConfiguration(ShardingConfigurationLoader.java:85) at org.apache.shardingsphere.shardingproxy.config.ShardingConfigurationLoader.load(ShardingConfigurationLoader.java:63) at org.apache.shardingsphere.shardingproxy.Bootstrap.main(Bootstrap.java:74) Caused by: Cannot create property=tables for JavaBean=org.apache.shardingsphere.core.yaml.config.sharding.YamlShardingRuleConfiguration@6302bbb1 in 'reader', line 502, column 3: tables: ^ No single argument constructor found for class org.apache.shardingsphere.core.yaml.config.sharding.YamlTableRuleConfiguration in 'reader', line 503, column 5: brand: ^ at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:312) at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.construct(Constructor.java:189) at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:182) at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:297) ``` with the error log above, I totally have no idea what's wrong in config file.
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