具名参数：

具名参数:SQL 按名称(以冒号开头)而不是按位置进行指定. 具名参数更易于维护, 也提升了可读性. 具名参数由框架类在运行时用占位符取代

我们之前一直是用JDBCTemplate  进行Sql语句的 拼写 ， 但是 当 一个行中有 多个 占位符时，很容易 搞混哪个值 是 哪个值。 那我们可以使用具名参数。

如何使用具名参数？

1. 在 xml 文件中加入对具名参数的支持

注意具名参数只能 使用 constructor-arg  并且必须对 dataSource 赋值

<!-- 具名参数 必须要有参数的构造器   没有无参的 -->
<bean id="namedParameterJdbcTemplate" class="org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate">
    <constructor-arg name="dataSource" ref="DataSource"></constructor-arg>
</bean>

applicationContext.xml

2. 在Java 类中引入 具名参数

import java.util.HashMap;
import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.jdbc.core.namedparam.EmptySqlParameterSource;
import org.springframework.jdbc.core.namedparam.MapSqlParameterSource;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
import org.springframework.jdbc.core.namedparam.SqlParameterSource;
import org.springframework.stereotype.Repository;

import com.myth.springJDBC.exception.AddFailedException;
import com.myth.springJDBC.po.Employee;

@Repository
public class EmployeeDao {
    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Autowired
    private NamedParameterJdbcTemplate namedParameterJdbcTemplate;

    private String sql;
    　　//这个使用的 是 传统的 JdbcTemplate
    public Employee getEmployee(int id) {
        sql = "Select * from employees where id = ?";
        RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<Employee>(Employee.class);
        Employee employee = jdbcTemplate.queryForObject(sql, rowMapper,id);
        return employee;
    }

    //引入一个 空 的Map EmptySqlParameterSource.INSTANCE
    public Integer getCount() {
        sql = "select count(*) from employees";
        int result = namedParameterJdbcTemplate.queryForObject(sql, EmptySqlParameterSource.INSTANCE, Integer.class);
        return result;
    }
    /*这里也可以使用BeanPropertySqlParameterSource     * 这个意思就是把Map 转换为对象 来对待      */
    public void insertEmployee(Employee employee) {
        sql = "INSERT INTO employees values (:ID,:ln,:email,:departID)";
        Map<String, Object> paramMap = new HashMap<>();
        paramMap.put("ID", employee.getId());
        paramMap.put("ln", employee.getLast_name());
        paramMap.put("email", employee.getEmail());
        paramMap.put("departID", employee.getDept_id());

        try {
            namedParameterJdbcTemplate.update(sql, paramMap);
            System.out.println("添加成功");
        } catch (Exception e) {
            throw new AddFailedException("添加失败");
        }
    }

　　 //要注意具名参数要和Bean中的属性值要一致。　　 public void updateEmployee(Employee employee) {　　　　  sql = "UPDATE employees set LAST_NAME =:last_name,EMAIL=:email,DEPT_ID =:dept_id WHERE ID = :id";　　　　  SqlParameterSource paramSource = new BeanPropertySqlParameterSource(employee);　　　　  try {　　　　   namedParameterJdbcTemplate.update(sql, paramSource);　　　　   System.out.println("修改成功");　　　　  } catch (Exception e) {　　　　   System.out.println(e.toString());　　　　   throw new AddFailedException("修改失败");　　　　  }　　　　 }　　　　/*    这样子 会报错
 * public void deleteEmployee(int id) {
        sql = "DELETE FROM EMPLOYEES WHERE ID = :ID";
        Map<String, Object> paramMap = new HashMap<>();
        paramMap.put("ID", id);
        try {
            namedParameterJdbcTemplate.update(sql, paramMap);
            System.out.println("删除成功");
        } catch (Exception e) {
            throw new AddFailedException("删除失败");
        }
    }*/
    //必须传入Employee   只传入int id 会报错
    public void deleteEmployee(Employee employee) {
        sql = "DELETE FROM EMPLOYEES WHERE ID = :ID";
        Map<String, Object> paramMap = new HashMap<>();
        paramMap.put("ID", employee.getId());
        try {
            namedParameterJdbcTemplate.update(sql, paramMap);
            System.out.println("删除成功");
        } catch (Exception e) {
            throw new AddFailedException("删除失败");
        }
    }
}

3.然后写Junit Test 类

 1 package com.myth.springJDBC;
 2
 3
 4 import org.junit.Test;
 5 import org.junit.runner.RunWith;
 6 import org.springframework.beans.factory.annotation.Autowired;
 7 import org.springframework.test.context.ContextConfiguration;
 8 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 9
10 import com.myth.springJDBC.dao.EmployeeDao;
11 import com.myth.springJDBC.po.Employee;
12 @RunWith(SpringJUnit4ClassRunner.class)
13 @ContextConfiguration(locations="classpath:applicationContext.xml")
14 public class TestJDBC {
15     @Autowired
16     private EmployeeDao employeeDao;
17
18     @Test
19     public void testQuery() {
20         System.out.println(employeeDao.getEmployee(12));
21     }
22
23     @Test
24     public void testInsert() {
25         Employee employee = new Employee();
26         employee.setId(12);
27         employee.setLast_name("FF");
28         employee.setEmail("[email protected]");
29         employee.setDept_id(4);
30
31         employeeDao.insertEmployee(employee);
32     }
33
34     @Test
35     public void testUpdate() {
36         Employee employee = new Employee();
37         employee.setId(12);
38         employee.setLast_name("FFF");
39         employee.setEmail("[email protected]");
40         employee.setDept_id(4);
41
42         employeeDao.updateEmployee(employee);
43     }
44
45     @Test
46     public void testDelete() {
47         Employee employee = new Employee();
48         employee.setId(12);
49         employeeDao.deleteEmployee(employee);
50     }
51
52     @Test
53     public void testGetCount() {
54         System.out.println(employeeDao.getCount());
55     }
56 }

Junit