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/*
* Copyright (c) "Neo4j"
* Neo4j Sweden AB [http://neo4j.com]
*
* This file is part of Neo4j.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.neo4j.driver;
import java.util.Map;
import org.neo4j.driver.async.AsyncSession;
import org.neo4j.driver.util.Resource;
/**
* Provides a context of work for database interactions.
*
* A Session is a logical container for a causally chained series of
* {@linkplain Transaction transactions}. Client applications typically work
* with managed transactions, which come in two flavours: transaction
* functions and auto-commit transactions. Managed transactions automatically
* handle the transaction boundaries (BEGIN and
* COMMIT/ROLLBACK) and can also provide other
* supporting features; transaction functions offer retry capabilities, for
* example.
*
* Unmanaged transactions are also available but tend to be used by libraries
* or tooling that require more fine-grained control.
*
* Typically, a session will acquire a TCP connection from a connection pool
* in order to carry out a transaction. Once the transaction has completed,
* and the entire result has been consumed, this connection will be released
* back into the pool. One connection can therefore be adopted by several
* sessions over its lifetime, although it will only be owned by one at a
* time. Client applications should never need to deal directly with
* connection management.
*
* Session implementations are not generally thread-safe. Therefore, multiple
* sessions should be used when an application requires multiple concurrent
* threads of database work to be carried out.
*
* @since 1.0 (Removed async API to {@link AsyncSession} in 4.0)
*/
public interface Session extends Resource, QueryRunner
{
/**
* Begin a new unmanaged {@linkplain Transaction transaction}. At
* most one transaction may exist in a session at any point in time. To
* maintain multiple concurrent transactions, use multiple concurrent
* sessions.
*
* @return a new {@link Transaction}
*/
Transaction beginTransaction();
/**
* Begin a new unmanaged {@linkplain Transaction transaction} with
* the specified {@link TransactionConfig configuration}. At most one
* transaction may exist in a session at any point in time. To maintain
* multiple concurrent transactions, use multiple concurrent sessions.
*
* @param config configuration for the new transaction.
* @return a new {@link Transaction}
*/
Transaction beginTransaction( TransactionConfig config );
/**
* Execute a unit of work in a managed {@link AccessMode#READ read} transaction.
*
* This transaction will automatically be committed unless an exception is
* thrown during query execution or by the user code.
*
* Managed transactions should not generally be explicitly committed (via
* {@link Transaction#commit()}).
*
* @param work the {@link TransactionWork} to be applied to a new read transaction.
* @param the return type of the given unit of work.
* @return a result as returned by the given unit of work.
*/
T readTransaction( TransactionWork work );
/**
* Execute a unit of work in a managed {@link AccessMode#READ read} transaction
* with the specified {@link TransactionConfig configuration}.
*
* This transaction will automatically be committed unless an exception is
* thrown during query execution or by the user code.
*
* Managed transactions should not generally be explicitly committed (via
* {@link Transaction#commit()}).
*
* @param work the {@link TransactionWork} to be applied to a new read transaction.
* @param config configuration for all transactions started to execute the unit of work.
* @param the return type of the given unit of work.
* @return a result as returned by the given unit of work.
*/
T readTransaction( TransactionWork work, TransactionConfig config );
/**
* Execute a unit of work in a managed {@link AccessMode#WRITE write} transaction.
*
* This transaction will automatically be committed unless an exception is
* thrown during query execution or by the user code.
*
* Managed transactions should not generally be explicitly committed (via
* {@link Transaction#commit()}).
*
* @param work the {@link TransactionWork} to be applied to a new write transaction.
* @param the return type of the given unit of work.
* @return a result as returned by the given unit of work.
*/
T writeTransaction( TransactionWork work );
/**
* Execute a unit of work in a managed {@link AccessMode#WRITE write} transaction
* with the specified {@link TransactionConfig configuration}.
*
* This transaction will automatically be committed unless an exception is
* thrown during query execution or by the user code.
*
* Managed transactions should not generally be explicitly committed (via
* {@link Transaction#commit()}).
*
* @param work the {@link TransactionWork} to be applied to a new write transaction.
* @param config configuration for all transactions started to execute the unit of work.
* @param the return type of the given unit of work.
* @return a result as returned by the given unit of work.
*/
T writeTransaction( TransactionWork work, TransactionConfig config );
/**
* Run a query in a managed auto-commit transaction with the specified
* {@link TransactionConfig configuration}, and return a result stream.
*
* @param query text of a Neo4j query.
* @param config configuration for the new transaction.
* @return a stream of result values and associated metadata.
*/
Result run(String query, TransactionConfig config );
/**
* Run a query with parameters in a managed auto-commit transaction with the
* specified {@link TransactionConfig configuration}, and return a result stream.
*
* This method takes a set of parameters that will be injected into the
* query by Neo4j. Using parameters is highly encouraged, it helps avoid
* dangerous cypher injection attacks and improves database performance as
* Neo4j can re-use query plans more often.
*
* This version of run takes a {@link Map} of parameters. The values in the map
* must be values that can be converted to Neo4j types. See {@link Values#parameters(Object...)} for
* a list of allowed types.
*
*
Example
*
* {@code
* Map metadata = new HashMap<>();
* metadata.put("type", "update name");
*
* TransactionConfig config = TransactionConfig.builder()
* .withTimeout(Duration.ofSeconds(3))
* .withMetadata(metadata)
* .build();
*
* Map parameters = new HashMap<>();
* parameters.put("myNameParam", "Bob");
*
* Result result = session.run("MATCH (n) WHERE n.name = $myNameParam RETURN (n)", parameters, config);
* }
*
*
* @param query text of a Neo4j query.
* @param parameters input data for the query.
* @param config configuration for the new transaction.
* @return a stream of result values and associated metadata.
*/
Result run(String query, Map parameters, TransactionConfig config );
/**
* Run a query in a managed auto-commit transaction with the specified
* {@link TransactionConfig configuration}, and return a result stream.
* Example
*
* {@code
* Map metadata = new HashMap<>();
* metadata.put("type", "update name");
*
* TransactionConfig config = TransactionConfig.builder()
* .withTimeout(Duration.ofSeconds(3))
* .withMetadata(metadata)
* .build();
*
* Query query = new Query("MATCH (n) WHERE n.name = $myNameParam RETURN n.age");
* Result result = session.run(query.withParameters(Values.parameters("myNameParam", "Bob")));
* }
*
*
* @param query a Neo4j query.
* @param config configuration for the new transaction.
* @return a stream of result values and associated metadata.
*/
Result run(Query query, TransactionConfig config );
/**
* Return the bookmark received following the last completed
* {@linkplain Transaction transaction}. If no bookmark was received
* or if this transaction was rolled back, the bookmark value will
* be null.
*
* @return a reference to a previous transaction
*/
Bookmark lastBookmark();
/**
* Reset the current session. This sends an immediate RESET signal to the server which both interrupts
* any query that is currently executing and ignores any subsequently queued queries. Following
* the reset, the current transaction will have been rolled back and any outstanding failures will
* have been acknowledged.
*
* @deprecated This method should not be used and violates the expected usage pattern of {@link Session} objects.
* They are expected to be not thread-safe and should not be shared between thread. However this method is only
* useful when {@link Session} object is passed to another monitoring thread that calls it when appropriate.
* It is not useful when {@link Session} is used in a single thread because in this case {@link #close()}
* can be used. Since version 3.1, Neo4j database allows users to specify maximum transaction execution time and
* contains procedures to list and terminate running queries. These functions should be used instead of calling
* this method.
*/
@Deprecated
void reset();
/**
* Signal that you are done using this session. In the default driver usage, closing and accessing sessions is
* very low cost.
*/
@Override
void close();
}