org.apache.tomcat.jdbc.pool

## Class JdbcInterceptor

- java.lang.Object
- - org.apache.tomcat.jdbc.pool.JdbcInterceptor

- All Implemented Interfaces:
    InvocationHandler
  Direct Known Subclasses:
    AbstractCreateStatementInterceptor, ConnectionState, DisposableConnectionFacade, ProxyConnection, TrapException

      public abstract class JdbcInterceptor
      extends Object
      implements InvocationHandler

  Abstract class that is to be extended for implementations of interceptors. Everytime an operation is called on the `Connection` object the `invoke(Object, Method, Object[])` method on the interceptor will be called. Interceptors are useful to change or improve behavior of the connection pool.
  Interceptors can receive a set of properties. Each sub class is responsible for parsing the properties during runtime when they are needed or simply override the `setProperties(Map)` method. Properties arrive in a key-value pair of Strings as they were received through the configuration. This method is called once per cached connection object when the object is first configured.
  Version:
    1.0

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static String` | `CLOSE_VAL` `Connection.close()` method name
    `static String` | `EQUALS_VAL` `Object.equals(Object)`
    `static String` | `GETCONNECTION_VAL` `PooledConnection.getConnection()` method name
    `static String` | `HASHCODE_VAL` `Object.hashCode()`
    `static String` | `ISCLOSED_VAL` `Connection.isClosed()` method name
    `static String` | `ISVALID_VAL` `Connection.isValid(int)` method name
    `static String` | `ISWRAPPERFOR_VAL` `Wrapper.isWrapperFor(Class)` method name
    `protected Map<String,PoolProperties.InterceptorProperty>` | `properties` Properties for this interceptor.
    `static String` | `TOSTRING_VAL` `Object.toString()` method name
    `static String` | `UNWRAP_VAL` `Wrapper.unwrap(Class)` method name

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `JdbcInterceptor()` Public constructor for instantiation through reflection

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `compare(String methodName, Method method)` Compares a method name (String) to a method (Method) `compare(String,String)` Uses reference comparison unless the useEquals property is set to true
    `boolean` | `compare(String name1, String name2)` Performs a string comparison, using references unless the useEquals property is set to true.
    `void` | `disconnected(ConnectionPool parent, PooledConnection con, boolean finalizing)` Called when `Connection.close()` is called on the underlying connection.
    `JdbcInterceptor` | `getNext()` Returns the next interceptor in the chain
    `Map<String,PoolProperties.InterceptorProperty>` | `getProperties()` Returns the properties configured for this interceptor
    `Object` | `invoke(Object proxy, Method method, Object[] args)` Gets invoked each time an operation on `Connection` is invoked.
    `boolean` | `isUseEquals()`
    `void` | `poolClosed(ConnectionPool pool)` This method is invoked by a connection pool when the pool is closed.
    `void` | `poolStarted(ConnectionPool pool)` This method is invoked by a connection pool when the pool is first started up, usually when the first connection is requested.
    `abstract void` | `reset(ConnectionPool parent, PooledConnection con)` Gets called each time the connection is borrowed from the pool This means that if an interceptor holds a reference to the connection the interceptor can be reused for another connection.
    `void` | `setNext(JdbcInterceptor next)` configures the next interceptor in the chain
    `void` | `setProperties(Map<String,PoolProperties.InterceptorProperty> properties)` Called during the creation of an interceptor The properties can be set during the configuration of an interceptor Override this method to perform type casts between string values and object properties
    `void` | `setUseEquals(boolean useEquals)` Set to true if string comparisons (for the `compare(String, Method)` and `compare(String, String)` methods) should use the Object.equals(Object) method The default is false

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### CLOSE_VAL

          public static final String CLOSE_VAL

      `Connection.close()` method name
      See Also:
        Constant Field Values

    - #### TOSTRING_VAL

          public static final String TOSTRING_VAL

      `Object.toString()` method name
      See Also:
        Constant Field Values

    - #### ISCLOSED_VAL

          public static final String ISCLOSED_VAL

      `Connection.isClosed()` method name
      See Also:
        Constant Field Values

    - #### GETCONNECTION_VAL

          public static final String GETCONNECTION_VAL

      `PooledConnection.getConnection()` method name
      See Also:
        Constant Field Values

    - #### UNWRAP_VAL

          public static final String UNWRAP_VAL

      `Wrapper.unwrap(Class)` method name
      See Also:
        Constant Field Values

    - #### ISWRAPPERFOR_VAL

          public static final String ISWRAPPERFOR_VAL

      `Wrapper.isWrapperFor(Class)` method name
      See Also:
        Constant Field Values

    - #### ISVALID_VAL

          public static final String ISVALID_VAL

      `Connection.isValid(int)` method name
      See Also:
        Constant Field Values

    - #### EQUALS_VAL

          public static final String EQUALS_VAL

      `Object.equals(Object)`
      See Also:
        Constant Field Values

    - #### HASHCODE_VAL

          public static final String HASHCODE_VAL

      `Object.hashCode()`
      See Also:
        Constant Field Values

    - #### properties

          protected Map<String,PoolProperties.InterceptorProperty> properties

      Properties for this interceptor.

  - ### Constructor Detail

    - #### JdbcInterceptor

          public JdbcInterceptor()

      Public constructor for instantiation through reflection

  - ### Method Detail

    - #### invoke

          public Object invoke(Object proxy,
                      Method method,
                      Object[] args)
                        throws Throwable

      Gets invoked each time an operation on `Connection` is invoked.
      Specified by:
        `invoke` in interface `InvocationHandler`
      Throws:
        `Throwable`

    - #### getNext

          public JdbcInterceptor getNext()

      Returns the next interceptor in the chain
      Returns:
        the next interceptor in the chain

    - #### setNext

          public void setNext(JdbcInterceptor next)

      configures the next interceptor in the chain
      Parameters:
        `next` - The next chain item

    - #### compare

          public boolean compare(String name1,
                        String name2)

      Performs a string comparison, using references unless the useEquals property is set to true.
      Parameters:
        `name1` - The first name
        `name2` - The second name
      Returns:
        true if name1 is equal to name2 based on `useEquals`

    - #### compare

          public boolean compare(String methodName,
                        Method method)

      Compares a method name (String) to a method (Method) `compare(String,String)` Uses reference comparison unless the useEquals property is set to true
      Parameters:
        `methodName` - The method name
        `method` - The method
      Returns:
        `true` if the name matches

    - #### reset

          public abstract void reset(ConnectionPool parent,
                   PooledConnection con)

      Gets called each time the connection is borrowed from the pool This means that if an interceptor holds a reference to the connection the interceptor can be reused for another connection.
      This method may be called with null as both arguments when we are closing down the connection.
      Parameters:
        `parent` - - the connection pool owning the connection
        `con` - - the pooled connection

    - #### disconnected

          public void disconnected(ConnectionPool parent,
                          PooledConnection con,
                          boolean finalizing)

      Called when `Connection.close()` is called on the underlying connection. This is to notify the interceptors, that the physical connection has been released. Implementation of this method should be thought through with care, as no actions should trigger an exception.
      Parameters:
        `parent` - - the connection pool that this connection belongs to
        `con` - - the pooled connection that holds this connection
        `finalizing` - - if this connection is finalizing. True means that the pooled connection will not reconnect the underlying connection

    - #### getProperties

          public Map<String,PoolProperties.InterceptorProperty> getProperties()

      Returns the properties configured for this interceptor
      Returns:
        the configured properties for this interceptor

    - #### setProperties

          public void setProperties(Map<String,PoolProperties.InterceptorProperty> properties)

      Called during the creation of an interceptor The properties can be set during the configuration of an interceptor Override this method to perform type casts between string values and object properties
      Parameters:
        `properties` - The properties

    - #### isUseEquals

          public boolean isUseEquals()

      Returns:
        true if the compare method uses the Object.equals(Object) method false if comparison is done on a reference level

    - #### setUseEquals

          public void setUseEquals(boolean useEquals)

      Set to true if string comparisons (for the `compare(String, Method)` and `compare(String, String)` methods) should use the Object.equals(Object) method The default is false
      Parameters:
        `useEquals` - `true` if equals will be used for comparisons

    - #### poolClosed

          public void poolClosed(ConnectionPool pool)

      This method is invoked by a connection pool when the pool is closed. Interceptor classes can override this method if they keep static variables or other tracking means around. This method is only invoked on a single instance of the interceptor, and not on every instance created.
      Parameters:
        `pool` - - the pool that is being closed.

    - #### poolStarted

          public void poolStarted(ConnectionPool pool)

      This method is invoked by a connection pool when the pool is first started up, usually when the first connection is requested. Interceptor classes can override this method if they keep static variables or other tracking means around. This method is only invoked on a single instance of the interceptor, and not on every instance created.
      Parameters:
        `pool` - - the pool that is being closed.

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