這裏有幾個例子來說明如何使用SimpleJdbcTemplate query()方法來查詢或從資料庫中提取數據。在 JdbcTemplate query() 方法，需要手動轉換返回的結果轉換為一個目標對象類型，並傳遞一個對象數組作為參數。在SimpleJdbcTemplate類，它是更加人性化和簡單。
1.查詢單行
這裏有向你展示了如何查詢或從資料庫中提取單行的兩種方式，並將其轉換成一個模型類。
1.1 自定義RowMapper
在一般情況下，它總是建議來實現 RowMapper 介面來創建自定義的RowMapper，以滿足您的需求。
package com.zaixian.customer.model;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.springframework.jdbc.core.RowMapper;
public class CustomerRowMapper implements RowMapper
{
public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
Customer customer = new Customer();
customer.setCustId(rs.getInt("CUST_ID"));
customer.setName(rs.getString("NAME"));
customer.setAge(rs.getInt("AGE"));
return customer;
}
}
public Customer findByCustomerId(int custId){
String sql = "SELECT * FROM CUSTOMER WHERE CUST_ID = ?";
Customer customer = getSimpleJdbcTemplate().queryForObject(
sql, new CustomerParameterizedRowMapper(), custId);
return customer;
}
1.2 BeanPropertyRowMapper
在SimpleJdbcTemplate類，需要使用“ParameterizedBeanPropertyRowMapper' 代替 'BeanPropertyRowMapper”。
public Customer findByCustomerId2(int custId){
String sql = "SELECT * FROM CUSTOMER WHERE CUST_ID = ?";
Customer customer = getSimpleJdbcTemplate().queryForObject(sql,
ParameterizedBeanPropertyRowMapper.newInstance(Customer.class), custId);
return customer;
}
2，查詢多行
從資料庫查詢或提取多行記錄，並將其轉換成一個列表。
2.1 ParameterizedBeanPropertyRowMapper
public List<Customer> findAll(){
String sql = "SELECT * FROM CUSTOMER";
List<Customer> customers =
getSimpleJdbcTemplate().query(sql,
ParameterizedBeanPropertyRowMapper.newInstance(Customer.class));
return customers;
}
3.查詢單值
查詢或提取資料庫中的單個列的值。
3.1單列名
它顯示了如何查詢單個列名作為字串。
public String findCustomerNameById(int custId){
String sql = "SELECT NAME FROM CUSTOMER WHERE CUST_ID = ?";
String name = getSimpleJdbcTemplate().queryForObject(
sql, String.class, custId);
return name;
}
3.2、行總數
它展示了如何從資料庫中查詢行的總數。
public int findTotalCustomer(){
String sql = "SELECT COUNT(*) FROM CUSTOMER";
int total = getSimpleJdbcTemplate().queryForInt(sql);
return total;
}
運行它
package com.xuhuhu.common;
import java.util.ArrayList;
import java.util.List;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.zaixian.customer.dao.CustomerDAO;
import com.zaixian.customer.model.Customer;
public class SimpleJdbcTemplateApp
{
public static void main( String[] args )
{
ApplicationContext context =
new ClassPathXmlApplicationContext("Spring-Customer.xml");
CustomerDAO customerSimpleDAO =
(CustomerDAO) context.getBean("customerSimpleDAO");
Customer customerA = customerSimpleDAO.findByCustomerId(1);
System.out.println("Customer A : " + customerA);
Customer customerB = customerSimpleDAO.findByCustomerId2(1);
System.out.println("Customer B : " + customerB);
List<Customer> customerAs = customerSimpleDAO.findAll();
for(Customer cust: customerAs){
System.out.println("Customer As : " + customerAs);
}
List<Customer> customerBs = customerSimpleDAO.findAll2();
for(Customer cust: customerBs){
System.out.println("Customer Bs : " + customerBs);
}
String customerName = customerSimpleDAO.findCustomerNameById(1);
System.out.println("Customer Name : " + customerName);
int total = customerSimpleDAO.findTotalCustomer();
System.out.println("Total : " + total);
}
}
總結
SimpleJdbcTemplate 是不能代替 JdbcTemplate 的，它只是一個Java5的友好補充它。