Javaweb Learning Note 8-dbutils Toolkit

In today's terms Javaweb 8th stage of learning. dbutils technology , Dbutils is a very common function of our database, although later use is its packaging results, but also need to master.

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A * Overview :

1* definition :

additions and deletions for encapsulation operations database .

* features :

A* read operations for data tables . Span style= "Font-family:times New Roman", He can convert the results to list array , set java collection Easy for programmers to manipulate

b* write operations for data tables , and it became easy . ( just write the SQL statement ).

c* can use data sources , Use JNDI, database connection pooling and other technologies to optimize performance .

two * Common class :

1* Queryrunner class :

1.1* Constructor :

* Queryrunner (): Default no parameter construction .

* Queryrunner (DataSource DS): The construction of the pass-through connection pool .

1.2* Common methods :

* query () Method : used to perform query operations

* query (Connection conn, String sql, resultsethandler<t> rsh, Object ... params)

* Query (String sql, resultsethandler<t> rsh, Object ... params)

* Update () method : used to perform additions, deletions and modifications .

* UPDATE (Connection conn, String sql, Object ... params)

* UPDATE (String sql, Object ... params)

Resultsethandler Interface :

handle (ResultSet Rs) method :

used to add ResultSet conversion of result set types .

three * Two ways of managing transactions :

1* Manually Manage Transactions :

* Queryrunner ()

* Query (Connection conn, String sql, resultsethandler<t> rsh, Object ... params)

* UPDATE (Connection conn, String sql, Object ... params)

* Tool Management Transactions :

* Queryrunner (DataSource DS)

* Query (String sql, resultsethandler<t> rsh, Object ... params)

* UPDATE (String sql, Object ... params)

Four * Resultsethandler:

through the above query statements can be found, every time to implement Resultsethandler the method is very troublesome. In fact , the Resultsethandler interface provides nine implementation classes for use, as follows:

1* Arrayhandler: Turns the first row of data in the result set into an array of objects .

2 * Arraylisthandler: Each row of data in the result set is converted into an array of objects and then stored in the list .

Beanhandler: Encapsulates the first row of data in the result set into a corresponding JavaBean instance .

Beanlisthandler: Encapsulates each row of data in the result set into a corresponding JavaBean instance and stores it in the list in .

5* Maphandler: Encapsulates the first row of data in the result set into a Map , where key is the column name , value is the corresponding value .

6* Maplisthandler: Each row of data in the result set is encapsulated in a Map and then stored in the List.

7* Columnlisthandler: The data from a column in the result set is stored in the list .

8* Keyedhandler: Encapsulates each row of data in the result set into a map , and then the map To a map and its key is the specified column .

9* Scalarhandler: Make a single value query .

Javaweb Learning Notes 8-dbutils Toolkit