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我们可以使用
JdbcTemplate 类的
query()方法轻松地从数据库中获取记录，我们需要传递ResultSetExtractor的实例。
public T query(String sql,ResultSetExtractor<T> rse)
ResultSetExtractor 接口可用于从数据库中获取记录。它接受一个ResultSet并返回列表。
它仅定义一个方法ResultResult实例作为参数接受。该方法的语法如下:
public T extractData(ResultSet rs)throws SQLException,DataAccessException
我们假设您已经在Oracle10g数据库中创建了以下表。
create table employee( id number(10) name varchar2(100), salary number(10) );
Employee.java
此类包含3一个带有构造函数，setter和getter的属性。它定义了一个额外的toString()方法。
package com.w3codebox;
public class Employee {
private int id;
private String name;
private float salary;
//no-arg and parameterized constructors
//getters and setters
public String toString(){
return id+" "+name+" "+salary;
}
}
EmployeeDao.java
它包含属性jdbcTemplate和一种方法getAllEmployees。
package com.w3codebox;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.ResultSetExtractor;
public class EmployeeDao {
private JdbcTemplate template;
public void setTemplate(JdbcTemplate template) {
this.template = template;
}
public List<Employee> getAllEmployees(){
return template.query("select * from employee",new ResultSetExtractor<List<Employee>>(){
@Override
public List<Employee> extractData(ResultSet rs) throws SQLException,
DataAccessException {
List<Employee> list=new ArrayList<Employee>();
while(rs.next()){
Employee e=new Employee();
e.setId(rs.getInt(1));
e.setName(rs.getString(2));
e.setSalary(rs.getInt(3));
list.add(e);
}
return list;
}
});
}
}
applicationContext.xml
DriverManagerDataSource usado para conter informações sobre o banco de dados, como o nome da classe do driver, a URL de conexão, o nome de usuário e a senha.
No JdbcTemplate do tipo DriverManagerDataSource há um método chamado
datasource A propriedade. Portanto, precisamos fornecer uma referência ao objeto DriverManagerDataSource para a propriedade do provedor de dados no JdbcTemplate.
Aqui, usamos o objeto JdbcTemplate na classe EmployeeDao, portanto, passamos por meio do método setter, mas você também pode usar o construtor.
<?xml version="1.0" encoding="UTF-8"?>
<beans
xmlns="http://www.springframework.org/schema/beans
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance
xmlns:p="http://www.springframework.org/schema/p
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<bean id="ds" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="oracle.jdbc.driver.OracleDriver"> />
<property name="url" value="jdbc:oracle:thin:@localhost:>1521:xe" />
<property name="username" value="system"> />
<property name="password" value="oracle"> />
</bean>
<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource" ref="ds"></property>
</bean>
<bean id="edao" class="com.w3codebox.EmployeeDao">
<property name="jdbcTemplate" ref="jdbcTemplate"></property>
</bean>
</beans>
Test.java
Este tipo obtém Beans do arquivo applicationContext.xml e chama o método getAllEmployees() da classe EmployeeDao.
package com.w3codebox;
import java.util.List;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Test {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
EmployeeDao dao = (EmployeeDao)ctx.getBean("edao");
List<Employee> list = dao.getAllEmployees();
for(Employee e:list)
System.out.println(e);
}
}