程序包 com.mysql.cj.xdevapi

接口 Session

  • 所有已知实现类:
    SessionImpl
    public interface Session
    X DevAPI introduces a new, high-level database connection concept that is called Session. When working with X DevAPI it is important to understand this new Session concept which is different from working with traditional low-level MySQL connections.

    An application using the Session class can be run against a single MySQL server or large number of MySQL servers forming a sharding cluster with no code changes.

    When using literal/verbatim SQL the common API patterns are mostly the same compared to using DML and CRUD operations on Tables and Collections. Two differences exist: setting the current schema and escaping names.

    You cannot call getSchema(String) or getDefaultSchema() to obtain a Schema object against which you can issue verbatin SQL statements. The Schema object does not feature a sql() function.

    The sql() function is a method of the Session class. Use sql(String) and the SQL command USE to change the current schema

    Session session = SessionFactory.getSession("root:s3kr3t@localhost");
    session.sql("USE test");

    If a Session has been established using a data source file the name of the default schema can be obtained to change the current database.

    Properties p = new Properties();
    p.setProperty("dataSourceFile", "/home/app_instance50/mysqlxconfig.json");
    Session session = SessionFactory.getSession(p);
    String defaultSchema = session.getDefaultSchema().getName();
    session.sql("USE ?").bind(defaultSchema).execute();

    A quoting function exists to escape SQL names/identifiers. StringUtils.quoteIdentifier(String, boolean) will escape the identifier given in accordance to the settings of the current connection. The escape function must not be used to escape values. Use the value bind syntax of sql(String) instead.

    // use bind syntax for values
    session.sql("DROP TABLE IF EXISTS ?").bind(name).execute();

    // use escape function to quote names/identifier
    var create = "CREATE TABLE ";
    create += StringUtils.quoteIdentifier(name, true);
    create += "(id INT NOT NULL PRIMARY KEY AUTO_INCREMENT");

    session.sql(create).execute();

    Users of the CRUD API do not need to escape identifiers. This is true for working with collections and for working with relational tables.

    • 方法详细资料

      • getSchemas

        List<Schema> getSchemas()
        Retrieve the list of Schema objects for which the current user has access.
        返回:
        list of Schema objects

      • getSchema

        Schema getSchema​(String schemaName)
        Retrieve the Schema corresponding to name.
        参数:
        schemaName - name of schema to retrieve
        返回:
        Schema

      • getDefaultSchemaName

        String getDefaultSchemaName()
        Retrieve the default schema name which may be configured at connect time.
        返回:
        default schema name

      • getDefaultSchema

        Schema getDefaultSchema()
        Retrieve the default schema which may be configured at connect time.
        返回:
        default Schema

      • createSchema

        Schema createSchema​(String schemaName)
        Create and return a new schema with the name given by name.
        参数:
        schemaName - name of schema to create
        返回:
        Schema created

      • createSchema

        Schema createSchema​(String schemaName,
                    boolean reuseExistingObject)
        Create and return a new schema with the name given by name. If the schema already exists, a reference to it is returned.
        参数:
        schemaName - name of schema to create
        reuseExistingObject - true to reuse
        返回:
        Schema created

      • dropSchema

        void dropSchema​(String schemaName)
        Drop the existing schema with the name given by name.
        参数:
        schemaName - name of schema to drop

      • getUri

        String getUri()
        Get the URL used to create this session.
        返回:
        URI

      • isOpen

        boolean isOpen()
        Is this session open?
        返回:
        true if session is open

      • close

        void close()
        Close this session.

      • startTransaction

        void startTransaction()
        Start a new transaction.

      • commit

        void commit()
        Commit the transaction.

      • rollback

        void rollback()
        Rollback the transaction.

      • setSavepoint

        String setSavepoint()
        Creates a transaction savepoint with an implementation-defined generated name and returns its name, which can be used in rollbackTo(String) or releaseSavepoint(String). Calling this method more than once should always work. The generated name shall be unique per session.
        返回:
        savepoint name

      • setSavepoint

        String setSavepoint​(String name)
        Creates or replaces a transaction savepoint with the given name. Calling this method more than once should always work.
        参数:
        name - savepoint name
        返回:
        savepoint name

      • rollbackTo

        void rollbackTo​(String name)
        Rolls back the transaction to the named savepoint. This method will succeed as long as the given save point has not been already rolled back or released. Rolling back to a savepoint prior to the one named will release or rollback any that came after.
        参数:
        name - savepoint name

      • releaseSavepoint

        void releaseSavepoint​(String name)
        Releases the named savepoint. This method will succeed as long as the given save point has not been already rolled back or released. Rolling back to a savepoint prior to the one named will release or rollback any that came after.
        参数:
        name - savepoint name

      • sql

        SqlStatement sql​(String sql)
        Create a native SQL command. Placeholders are supported using the native "?" syntax.
        参数:
        sql - native SQL statement
        返回:
        SqlStatement