Spring JdbcTemplate查詢實例

這裏有幾個例子向您展示如何使用JdbcTemplate的query()方法來查詢或從數據庫提取數據。整個項目的目錄結構如下：

1.查詢單行數據

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這裏有兩種方法來查詢或從數據庫中提取單行記錄，並將其轉換成一個模型類。

1.1 自定義RowMapper

在一般情況下，它總是建議實現 RowMapper 接口來創建自定義的RowMapper，以滿足您的需求。

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;
}

}

它傳遞給 queryForObject()方法，返回的結果將調用自定義 mapRow()方法的值匹配到屬性。

public Customer findByCustomerId(int custId){

String sql = "SELECT \* FROM CUSTOMER WHERE CUST\_ID = ?";

Customer customer = (Customer)getJdbcTemplate().queryForObject(
        sql, new Object\[\] { custId }, new CustomerRowMapper());

return customer;

}

1.2 BeanPropertyRowMapper

在Spring2.5中，帶有一個方便 RowMapper 實現所謂「BeanPropertyRowMapper」，它可以通過匹配行的名字的列值映射到一個屬性。只要確保這兩個屬性和列具有相同的名稱，如屬性「CUSTID'將匹配到列名爲：」CUSTID'或下劃線「CUST_ID」。

public Customer findByCustomerId2(int custId){

String sql = "SELECT \* FROM CUSTOMER WHERE CUST\_ID = ?";

Customer customer = (Customer)getJdbcTemplate().queryForObject(
        sql, new Object\[\] { custId }, 
        new BeanPropertyRowMapper(Customer.class));

return customer;

}

2，查詢多行

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現在，查詢或從數據庫中提取多行，並且將它轉換成一個列表。

2.1手動映射它

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返回多行，RowMapper 不支持 queryForList()方法，需要手動映射它。

public List findAll(){

String sql = "SELECT \* FROM CUSTOMER";

List<Customer> customers = new ArrayList<Customer>();

List<Map> rows = getJdbcTemplate().queryForList(sql);
for (Map row : rows) {
    Customer customer = new Customer();
    customer.setCustId((Long)(row.get("CUST\_ID")));
    customer.setName((String)row.get("NAME"));
    customer.setAge((Integer)row.get("AGE"));
    customers.add(customer);
}

return customers;

}

2.2 BeanPropertyRowMapper

最簡單的解決方案是使用 BeanPropertyRowMapper 類。

public List findAll(){

String sql = "SELECT \* FROM CUSTOMER";

List<Customer> customers  = getJdbcTemplate().query(sql,
        new BeanPropertyRowMapper(Customer.class));

return customers;

}

3.查詢單值

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在這個例子中，展示瞭如何從數據庫中查詢或提取單個列值。

3.1單列名

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它顯示瞭如何查詢單個列名作爲字符串。

public String findCustomerNameById(int custId){

String sql = "SELECT NAME FROM CUSTOMER WHERE CUST\_ID = ?";

String name = (String)getJdbcTemplate().queryForObject(
        sql, new Object\[\] { custId }, String.class);

return name;

}

3.2、行總數

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它展示瞭如何從數據庫中查詢行的總數。

public int findTotalCustomer(){

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

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

return total;

}

運行它

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 JdbcTemplateApp
{
public static void main( String[] args )
{
ApplicationContext context =
new ClassPathXmlApplicationContext("Spring-Customer.xml");

     CustomerDAO customerDAO = (CustomerDAO) context.getBean("customerDAO");

     Customer customerA = customerDAO.findByCustomerId(1);
     System.out.println("Customer A : " + customerA);

     Customer customerB = customerDAO.findByCustomerId2(1);
     System.out.println("Customer B : " + customerB);

     List<Customer> customerAs = customerDAO.findAll();
     for(Customer cust: customerAs){
          System.out.println("Customer As : " + customerAs);
     }

     List<Customer> customerBs = customerDAO.findAll2();
     for(Customer cust: customerBs){
          System.out.println("Customer Bs : " + customerBs);
     }

     String customerName = customerDAO.findCustomerNameById(1);
     System.out.println("Customer Name : " + customerName);

     int total = customerDAO.findTotalCustomer();
     System.out.println("Total : " + total);

}

}

總結

JdbcTemplate類，附帶了很多有用的重載查詢方法。它提醒參考現有的查詢方法在創建自己的自定義查詢方法之前，因爲 Spring 已經做給你了。

下載代碼 –   http://pan.baidu.com/s/1gecQHmN