Detailed explanation of dbutils toolkit for java learning notes

Dbutils Toolkit

I introduce

Dbutils is an open source database tool class of Apache organization.

II Use steps

①. Create queryrunner object

②. Call the update () method or query () method to execute SQL statements

III Construction method and static method

Queryrunner class

1. Construction method

①. Nonparametric structure

When using parameterless construction, you need to use the overloaded form with connection type parameters when calling the update method and query method

②. Parametric structure

This parameter is the connection pool object

2. Static method

①. int update(Connection con,String sql,Param);

This method is used to add, delete and modify statements

Parameter introduction:

Parameter 1: connection pool object (this is used in parameterless construction)

Parameter 2: SQL statement

Parameter 3: variable parameter (that is, the value of SQL placeholder)

Return value: the number of rows affected by int type

Simple update demo

Attach a simple c3p0 tool class

②. query(Connection con,Param ...)

This method is used for query operation

Parameter introduction:

Parameter 1: connection database connection object, which can be used without parameter construction

Parameter 2: SQL statement

Parameter 3: indicates the processing method of the result set (resultsethandler interface)

Arrayhandler: indicates that the data of the first row of the result set is stored in the array

Arraylisthandler stores the data of each row of the result set into an array, and multiple arrays into the set list < object [] >

Beanhandler means to store the data of the first row of the result set into a java bean object

Beanlisthandler means that the data of each row of the result set is stored in the Java Bean object, and multiple objects are stored in the collection

Columnlisthandler means to store the data of a column into a collection

Maphandler means to store the data of the first row of the result set into the map set: key: column name value: column value

Maplisthandler means that the data of each row of the result set is stored in the map set, and multiple maps are stored in the list set list < map <, > >

Scalarhandler gets a value: count (*) sum (price)

Parameter 4: variable parameter (that is, the value of SQL placeholder)

Demo using beanlisthandler processing method:

JavaBean class writing:

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