Spring Framework Module 4 – DAO, JDBC презентация

Insert / Update / Delete
JdbcTemplate :: Other SQL queries

data handling;
Makes it easy to work with such technologies as JDBC, Hibernate, JDO, etc.;
Allows to switch between technologies fairly easy;
Facilitates handling specific exceptions;

database;
The code is simplified and business objects are explicit;
Shipping from one DB (ORM, etc.) to another one is made easier;
Data access mechanism is accumulated at separate level;

all RDBMS possibilities
JDBC transparence – everything is under the control
Perfomance
No magic

Why (plain) JDBC is not enough?
Manual exception handling
Manual transaction management
No mapping of data to the objects
Big amount of the service code

Specify the statement;
Prepare and execute the statement;
Iteration through the results;
Do the work for each iteration;
Process any exception;
Handle transactions;
Close the connection;

With Spring support:
Specify the statement;
Do the work for each iteration;

controls database connections;
JdbcTemplate is a central class that control queries execution;
RowMapper: controls mapping of each query row;
JdbcDaoSupport: facilitates configuring and transferring parameters;

that can be seen as connection factory;
Spring connects the database via DataSource;
DataSource allows to hide connection pooling and transaction management;

testing easier;
Web container is not required;
Via JNDI;
Using DataSource implementations:
Apache DBCP;
c3p0 is the most useful implementation;

the connection from the pool
Opening the connection takes the time
If all opened connections are busy then new connection is created
As soon as user free up the connection it becomes available for other users
If the connection is not used it’s closing

Spring :: Retrieving javax.sql.DataSource

name="username" value="root"/>


OR
jndi-name="java:comp/env/jdbc/datasource"/>

database up in context (HSQLDB / H2 / Derby). HSQLDB is used by default.

или

SQL queries;
Iterates over results;
Catches JDBC exceptions;
Parameters necessary when executing SQL query:
DataSource;
RowMapper;
SQL query row;

once and then be used in various DAO;
DataSource is needed to create JdbcTemplate;
Generally, DataSource is transferred to DAO and then to JdbcTemplate;

data from DB to the object model

RowMapper is doing mapping of ResultSet to the certain objects

ResultSet

RowMapper

Book mapRow(ResultSet rs, int rowNum)

timestamp

Mapping data from object model to SQL

PreparedStatementSetter is doing mapping of object to SQL request

SQL

PreparedStatement

getPreparedStatementSetter
(final Book book)

+

specific objects;
Describes operations for each ResultSet row;
Used in query() method from JdbcTemplate or for results of stored procedure;

DataSource to DAO;
Implement RowMapper;
Create the JdbcTemplate instance;
Transfer DataSource there;
Invoke query() method;
Parameters: SQL query and RowMapper;

objects of Country type.

method will be already implemented;
JdbcDaoSupport facilitates working with DataSource and hides how JdbcTemplate is created;

to set datasource here
public void insert(Customer customer) {
String sql = "INSERT INTO CUSTOMER (CUST_ID, NAME, AGE) “+
”VALUES (?, ?, ?) »;
getJdbcTemplate().update(sql, new Object[] { customer.getCustId(),
customer.getName(),customer.getAge()
});
}

class="org.springframework.jdbc.datasource.DriverManagerDataSource">

Spring :: JdbcDaoSupport

the same way;
The only difference is SQL query;

be used when executing any SQL query:

to its own exception class hierarchy with the DataAccessException as the root exception;
Spring can also wrap checked exceptions specific to Hibernate, JDO, and JPA, and convert them to runtime exceptions;

extends SQLErrorCodeSQLExceptionTranslator {
protected DataAccessException customTranslate(String task, String sql, SQLException sqlex) {
if (sqlex.getErrorCode() == -12345) {
return new DeadlockLoserDataAccessException(task, sqlex);
}
return null;
}
}

private JdbcTemplate jdbcTemoplate;

public void setDataSource(DataSource dataSource) {
this.jdbcTemplate = new JdbcTemplate();
this.jdbcTemplate.setDataSource(dataSource);
CustomSQLErrorCodesTranslator tr = new CustomSQLErrorCodesTranslator();
tr.setDataSource(dataSource);
this.jdbcTemplate.setExceptionTranslator(tr);
}

Spring :: Custom DAO exceptions translator

min for practice;
15 min for discussion;