26: Leave connection creation to dialects (#27)

Task-Url: http://github.com/exasol/virtual-schema-common-jdbc/issues/26
exasol · Feb 4, 2020 · 3e2f564 · 3e2f564
1 parent 1777376
commit 3e2f564
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Showing 17 changed files with 156 additions and 147 deletions.
diff --git a/pom.xml b/pom.xml
@@ -9,7 +9,7 @@
     <description>Common module for JDBC-based data access from Virtual Schemas.</description>
     <url>https://github.com/exasol/virtual-schema-common-jdbc</url>
     <properties>
-        <product.version>2.2.1</product.version>
+        <product.version>3.0.0</product.version>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
         <java.version>11</java.version>

diff --git a/src/main/java/com/exasol/adapter/dialects/AbstractSqlDialect.java b/src/main/java/com/exasol/adapter/dialects/AbstractSqlDialect.java
@@ -2,7 +2,6 @@
 
 import static com.exasol.adapter.AdapterProperties.*;
 
-import java.sql.Connection;
 import java.sql.SQLException;
 import java.util.*;
 import java.util.logging.Logger;
@@ -12,6 +11,7 @@
 import com.exasol.ExaMetadata;
 import com.exasol.adapter.AdapterException;
 import com.exasol.adapter.AdapterProperties;
+import com.exasol.adapter.jdbc.ConnectionFactory;
 import com.exasol.adapter.jdbc.RemoteMetadataReader;
 import com.exasol.adapter.metadata.SchemaMetadata;
 import com.exasol.adapter.sql.*;
@@ -21,25 +21,21 @@
  */
 public abstract class AbstractSqlDialect implements SqlDialect {
     protected Set<ScalarFunction> omitParenthesesMap = EnumSet.noneOf(ScalarFunction.class);
-    protected RemoteMetadataReader remoteMetadataReader;
     protected AdapterProperties properties;
-    protected final Connection connection;
-    protected QueryRewriter queryRewriter;
+    protected final ConnectionFactory connectionFactory;
     private static final Pattern BOOLEAN_PROPERTY_VALUE_PATTERN = Pattern.compile("^TRUE$|^FALSE$",
             Pattern.CASE_INSENSITIVE);
     private static final Logger LOGGER = Logger.getLogger(AbstractSqlDialect.class.getName());
 
     /**
      * Create a new instance of an {@link AbstractSqlDialect}.
      *
-     * @param connection JDBC connection to remote data source
-     * @param properties user properties
+     * @param connectionFactory factory for JDBC connection to remote data source
+     * @param properties        user properties
      */
-    public AbstractSqlDialect(final Connection connection, final AdapterProperties properties) {
-        this.connection = connection;
+    public AbstractSqlDialect(final ConnectionFactory connectionFactory, final AdapterProperties properties) {
+        this.connectionFactory = connectionFactory;
         this.properties = properties;
-        this.remoteMetadataReader = createRemoteMetadataReader();
-        this.queryRewriter = createQueryRewriter();
     }
 
     /**
@@ -109,17 +105,17 @@ public Map<ScalarFunction, String> getPrefixFunctionAliases() {
     @Override
     public String rewriteQuery(final SqlStatement statement, final ExaMetadata exaMetadata)
             throws AdapterException, SQLException {
-        return this.queryRewriter.rewrite(statement, exaMetadata, this.properties);
+        return createQueryRewriter().rewrite(statement, exaMetadata, this.properties);
     }
 
     @Override
     public SchemaMetadata readSchemaMetadata() throws SQLException {
-        return this.remoteMetadataReader.readRemoteSchemaMetadata();
+        return createRemoteMetadataReader().readRemoteSchemaMetadata();
     }
 
     @Override
     public SchemaMetadata readSchemaMetadata(final List<String> tables) {
-        return this.remoteMetadataReader.readRemoteSchemaMetadata(tables);
+        return createRemoteMetadataReader().readRemoteSchemaMetadata(tables);
     }
 
     @Override
@@ -282,4 +278,4 @@ protected void validateCastNumberToDecimalProperty(final String castNumberToDeci
             }
         }
     }
-}
+}
diff --git a/src/main/java/com/exasol/adapter/dialects/BaseQueryRewriter.java b/src/main/java/com/exasol/adapter/dialects/BaseQueryRewriter.java
@@ -1,6 +1,5 @@
 package com.exasol.adapter.dialects;
 
-import java.sql.Connection;
 import java.sql.SQLException;
 import java.util.logging.Logger;
 
@@ -18,21 +17,21 @@ public class BaseQueryRewriter implements QueryRewriter {
     private static final Logger LOGGER = Logger.getLogger(BaseQueryRewriter.class.getName());
     protected final SqlDialect dialect;
     protected final RemoteMetadataReader remoteMetadataReader;
-    protected final Connection connection;
+    protected final ConnectionFactory connectionFactory;
     protected final ConnectionDefinitionBuilder connectionDefinitionBuilder;
 
     /**
      * Create a new instance of a {@link BaseQueryRewriter}.
      *
      * @param dialect              dialect
      * @param remoteMetadataReader remote metadata reader
-     * @param connection           JDBC connection to remote data source
+     * @param connectionFactory    JDBC connection to remote data source
      */
     public BaseQueryRewriter(final SqlDialect dialect, final RemoteMetadataReader remoteMetadataReader,
-            final Connection connection) {
+            final ConnectionFactory connectionFactory) {
         this.dialect = dialect;
         this.remoteMetadataReader = remoteMetadataReader;
-        this.connection = connection;
+        this.connectionFactory = connectionFactory;
         this.connectionDefinitionBuilder = createConnectionDefinitionBuilder();
     }
 
@@ -71,10 +70,10 @@ private String createPushdownQuery(final SqlStatement statement, final AdapterPr
         return pushdownQuery;
     }
 
-    private String createImportColumnsDescription(final String query) {
+    private String createImportColumnsDescription(final String query) throws SQLException {
         final ColumnMetadataReader columnMetadataReader = this.remoteMetadataReader.getColumnMetadataReader();
-        final ResultSetMetadataReader resultSetMetadataReader = new ResultSetMetadataReader(this.connection,
-                columnMetadataReader);
+        final ResultSetMetadataReader resultSetMetadataReader = new ResultSetMetadataReader(
+                this.connectionFactory.getConnection(), columnMetadataReader);
         final String columnsDescription = resultSetMetadataReader.describeColumns(query);
         LOGGER.finer(() -> "Import columns: " + columnsDescription);
         return columnsDescription;

diff --git a/src/main/java/com/exasol/adapter/dialects/SqlDialectFactory.java b/src/main/java/com/exasol/adapter/dialects/SqlDialectFactory.java
@@ -1,8 +1,7 @@
 package com.exasol.adapter.dialects;
 
-import java.sql.Connection;
-
 import com.exasol.adapter.AdapterProperties;
+import com.exasol.adapter.jdbc.ConnectionFactory;
 
 /**
  * This is the common interface for all factories that produce SQL dialects.
@@ -11,11 +10,11 @@ public interface SqlDialectFactory {
     /**
      * Create an instance of the SQL dialect adapter matching the dialect name.
      *
-     * @param connection JDBC connection to the remote data source
-     * @param properties user-defined adapter properties
+     * @param connectionFactory Factory for JDBC connection to the remote data source
+     * @param properties        user-defined adapter properties
      * @return SQL dialect adapter
      */
-    public SqlDialect createSqlDialect(final Connection connection, final AdapterProperties properties);
+    public SqlDialect createSqlDialect(final ConnectionFactory connectionFactory, final AdapterProperties properties);
 
     /**
      * Get the name of the SQL dialect this factory can produce.
@@ -30,4 +29,4 @@ public interface SqlDialectFactory {
      * @return SQL dialect version
      */
     public String getSqlDialectVersion();
-}
+}
diff --git a/src/main/java/com/exasol/adapter/dialects/SqlDialectRegistry.java b/src/main/java/com/exasol/adapter/dialects/SqlDialectRegistry.java
@@ -1,11 +1,11 @@
 package com.exasol.adapter.dialects;
 
-import java.sql.Connection;
 import java.util.*;
 import java.util.logging.Logger;
 import java.util.stream.Collectors;
 
 import com.exasol.adapter.AdapterProperties;
+import com.exasol.adapter.jdbc.ConnectionFactory;
 
 /**
  * This class implements a registry for supported SQL dialects.
@@ -72,18 +72,18 @@ public Set<String> getRegisteredAdapterNames() {
     /**
      * Get the SQL dialect registered under the given name.
      *
-     * @param name       name of the SQL dialect
-     * @param connection JDBC connection to the remote data source
-     * @param properties user-defined adapter properties
+     * @param name              name of the SQL dialect
+     * @param connectionFactory factory for JDBC connection to the remote data source
+     * @param properties        user-defined adapter properties
      * @return dialect instance
      */
-    public SqlDialect getDialectForName(final String name, final Connection connection,
+    public SqlDialect getDialectForName(final String name, final ConnectionFactory connectionFactory,
             final AdapterProperties properties) {
         if (hasDialectWithName(name)) {
             final SqlDialectFactory factory = this.registeredFactories.get(name);
             LOGGER.config(() -> "Loading SQL dialect: " + factory.getSqlDialectName() + " dialect adapter "
                     + factory.getSqlDialectVersion());
-            return factory.createSqlDialect(connection, properties);
+            return factory.createSqlDialect(connectionFactory, properties);
         } else {
             throw new IllegalArgumentException("Unknown SQL dialect \"" + name + "\" requested. " + describe());
         }

diff --git a/src/main/java/com/exasol/adapter/jdbc/ConnectionFactory.java b/src/main/java/com/exasol/adapter/jdbc/ConnectionFactory.java
@@ -0,0 +1,17 @@
+package com.exasol.adapter.jdbc;
+
+import java.sql.Connection;
+import java.sql.SQLException;
+
+/**
+ * Interface for factories creating custom JDBC connections.
+ */
+public interface ConnectionFactory {
+    /**
+     * Create a JDBC connection to the remote data source.
+     *
+     * @return JDBC connection to remote data source
+     * @throws SQLException if the connection to the remote source could not be established
+     */
+    Connection getConnection() throws SQLException;
+}
diff --git a/src/main/java/com/exasol/adapter/jdbc/JdbcAdapter.java b/src/main/java/com/exasol/adapter/jdbc/JdbcAdapter.java
@@ -1,6 +1,5 @@
 package com.exasol.adapter.jdbc;
 
-import java.sql.Connection;
 import java.sql.SQLException;
 import java.util.*;
 import java.util.logging.Logger;
@@ -24,7 +23,6 @@ public class JdbcAdapter implements VirtualSchemaAdapter {
     private static final String LITERAL_PREFIX = "LITERAL_";
     private static final String TABLES_PROPERTY = "TABLE_FILTER";
     private static final Logger LOGGER = Logger.getLogger(JdbcAdapter.class.getName());
-    private final RemoteConnectionFactory connectionFactory = new RemoteConnectionFactory();
 
     @Override
     public CreateVirtualSchemaResponse createVirtualSchema(final ExaMetadata exasolMetadata,
@@ -51,30 +49,28 @@ private AdapterProperties getPropertiesFromRequest(final AdapterRequest request)
     private SchemaMetadata readMetadata(final AdapterProperties properties, final ExaMetadata exasolMetadata)
             throws SQLException, PropertyValidationException {
         final List<String> tables = properties.getFilteredTables();
-        try (final Connection connection = this.connectionFactory.createConnection(exasolMetadata, properties)) {
-            final SqlDialect dialect = createDialect(connection, properties);
-            dialect.validateProperties();
-            if (tables.isEmpty()) {
-                return dialect.readSchemaMetadata();
-            } else {
-                return dialect.readSchemaMetadata(tables);
-            }
+        final ConnectionFactory connectionFactory = new RemoteConnectionFactory(exasolMetadata, properties);
+        final SqlDialect dialect = createDialect(connectionFactory, properties);
+        dialect.validateProperties();
+        if (tables.isEmpty()) {
+            return dialect.readSchemaMetadata();
+        } else {
+            return dialect.readSchemaMetadata(tables);
         }
     }
 
     protected SchemaMetadata readMetadata(final AdapterProperties properties,
             final List<String> whiteListedRemoteTables, final ExaMetadata exasolMetadata)
-            throws SQLException, PropertyValidationException {
-        try (final Connection connection = this.connectionFactory.createConnection(exasolMetadata, properties)) {
-            final SqlDialect dialect = createDialect(connection, properties);
-            dialect.validateProperties();
-            return dialect.readSchemaMetadata(whiteListedRemoteTables);
-        }
+            throws PropertyValidationException {
+        final ConnectionFactory connectionFactory = new RemoteConnectionFactory(exasolMetadata, properties);
+        final SqlDialect dialect = createDialect(connectionFactory, properties);
+        dialect.validateProperties();
+        return dialect.readSchemaMetadata(whiteListedRemoteTables);
     }
 
-    private SqlDialect createDialect(final Connection connection, final AdapterProperties properties) {
+    private SqlDialect createDialect(final ConnectionFactory connectionFactory, final AdapterProperties properties) {
         final String dialectName = properties.getSqlDialect();
-        return SqlDialectRegistry.getInstance().getDialectForName(dialectName, connection, properties);
+        return SqlDialectRegistry.getInstance().getDialectForName(dialectName, connectionFactory, properties);
     }
 
     @Override
@@ -117,15 +113,7 @@ public SetPropertiesResponse setProperties(final ExaMetadata metadata, final Set
         final AdapterProperties mergedProperties = new AdapterProperties(mergedRawProperties);
         if (AdapterProperties.isRefreshingVirtualSchemaRequired(requestRawProperties)) {
             final List<String> tableFilter = getTableFilter(mergedRawProperties);
-            final SchemaMetadata remoteMeta;
-            try {
-                remoteMeta = readMetadata(mergedProperties, tableFilter, metadata);
-            } catch (final SQLException exception) {
-                throw new AdapterException("Unable to set new properties for the virtual schema \""
-                        + schemaMetadataInfo.getSchemaName()
-                        + ("\", because metadata of the remote source could not be read. Cause: \" + exception.getMessage()"),
-                        exception);
-            }
+            final SchemaMetadata remoteMeta = readMetadata(mergedProperties, tableFilter, metadata);
             return SetPropertiesResponse.builder().schemaMetadata(remoteMeta).build();
         }
         return SetPropertiesResponse.builder().schemaMetadata(null).build();
@@ -162,19 +150,15 @@ public GetCapabilitiesResponse getCapabilities(final ExaMetadata exaMetadata, fi
             throws AdapterException {
         LOGGER.fine(() -> "Received request to list the adapter's capabilites.");
         final AdapterProperties properties = getPropertiesFromRequest(request);
-        try (final Connection connection = this.connectionFactory.createConnection(exaMetadata, properties)) {
-            final SqlDialect dialect = createDialect(connection, properties);
-            final Capabilities capabilities = dialect.getCapabilities();
-            final Capabilities excludedCapabilities = getExcludedCapabilities(properties);
-            capabilities.subtractCapabilities(excludedCapabilities);
-            return GetCapabilitiesResponse //
-                    .builder()//
-                    .capabilities(capabilities)//
-                    .build();
-        } catch (final SQLException exception) {
-            throw new AdapterException(
-                    "Unable to execute request to get capabilities. Cause: " + exception.getMessage(), exception);
-        }
+        final ConnectionFactory connectionFactory = new RemoteConnectionFactory(exaMetadata, properties);
+        final SqlDialect dialect = createDialect(connectionFactory, properties);
+        final Capabilities capabilities = dialect.getCapabilities();
+        final Capabilities excludedCapabilities = getExcludedCapabilities(properties);
+        capabilities.subtractCapabilities(excludedCapabilities);
+        return GetCapabilitiesResponse //
+                .builder()//
+                .capabilities(capabilities)//
+                .build();
     }
 
     private Capabilities getExcludedCapabilities(final AdapterProperties properties) {
@@ -219,9 +203,10 @@ private Capabilities.Builder parseExcludedCapabilities(final String excludedCapa
     @Override
     public PushDownResponse pushdown(final ExaMetadata exaMetadata, final PushDownRequest request)
             throws AdapterException {
-        final AdapterProperties properties = getPropertiesFromRequest(request);
-        try (final Connection connection = this.connectionFactory.createConnection(exaMetadata, properties)) {
-            final SqlDialect dialect = createDialect(connection, properties);
+        try {
+            final AdapterProperties properties = getPropertiesFromRequest(request);
+            final ConnectionFactory connectionFactory = new RemoteConnectionFactory(exaMetadata, properties);
+            final SqlDialect dialect = createDialect(connectionFactory, properties);
             final String importFromPushdownQuery = dialect.rewriteQuery(request.getSelect(), exaMetadata);
             return PushDownResponse.builder().pushDownSql(importFromPushdownQuery).build();
         } catch (final SQLException exception) {