Spring SimpleJdbcTemplate查询示例

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这里有几个例子来说明如何使用SimpleJdbcTemplate query()方法来查询或从数据库中提取数据。在 JdbcTemplate query() 方法，需要手动转换返回的结果转换为一个目标对象类型，并传递一个对象数组作为参数。在SimpleJdbcTemplate类，它是更加人性化和简单。

jdbctemplate VS simplejdbctemplate
请比较JdbcTemplate类的示例和SimpleJdbcTemplate类的示例。

1.查询单行

这里有向你展示了如何查询或从数据库中提取单行的两种方式，并将其转换成一个模型类。

1.1 自定义RowMapper

在一般情况下，它总是建议来实现 RowMapper 接口来创建自定义的RowMapper，以满足您的需求。

package com.yiibai.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类，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，查询多行

从数据库查询或提取多行记录，并将其转换成一个列表。

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.查询单值

查询或提取数据库中的单个列的值。

3.1单列名

它显示了如何查询单个列名作为字符串。

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、行总数

它展示了如何从数据库中查询行的总数。

public int findTotalCustomer(){

	String sql = "SELECT COUNT(*) FROM CUSTOMER";

	int total = getSimpleJdbcTemplate().queryForInt(sql);

	return total;

}

运行它

package com.yiibai.common;

import java.util.ArrayList;

import java.util.List;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.yiibai.customer.dao.CustomerDAO;

import com.yiibai.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);

    }

}