初探MyBatis之HelloWorld

Posted 2020-09-11

二、不使用 XML 构建 SqlSessionFactory

不使用xml构建SqlSessionFactory的话，就要用java代码来连接数据库。我这里直接new DataSorce()接口实现getConnection()方法（不知道对不对，反正实验证明，可行）。

EmployeeDataSourceFactory.java：

 1 package yyc.mybatis.util;
 2 
 3 import java.io.PrintWriter;
 4 import java.sql.Connection;
 5 import java.sql.DriverManager;
 6 import java.sql.SQLException;
 7 import java.sql.SQLFeatureNotSupportedException;
 8 import java.util.logging.Logger;
 9 
10 import javax.sql.DataSource;
11 
12 public class EmployeeDataSourceFactory {
13     
14     public static DataSource getEmployeeDataSorce(){
15         DataSource ds=new DataSource() {
16             
17             public <T> T unwrap(Class<T> iface) throws SQLException {
18                 // TODO Auto-generated method stub
19                 return null;
20             }
21             
22             public boolean isWrapperFor(Class<?> iface) throws SQLException {
23                 // TODO Auto-generated method stub
24                 return false;
25             }
26             
27             public void setLoginTimeout(int seconds) throws SQLException {
28                 // TODO Auto-generated method stub
29                 
30             }
31             
32             public void setLogWriter(PrintWriter out) throws SQLException {
33                 // TODO Auto-generated method stub
34                 
35             }
36             
37             public Logger getParentLogger() throws SQLFeatureNotSupportedException {
38                 // TODO Auto-generated method stub
39                 return null;
40             }
41             
42             public int getLoginTimeout() throws SQLException {
43                 // TODO Auto-generated method stub
44                 return 0;
45             }
46             
47             public PrintWriter getLogWriter() throws SQLException {
48                 // TODO Auto-generated method stub
49                 return null;
50             }
51             
52             public Connection getConnection(String username, String password) throws SQLException {
53                 // TODO Auto-generated method stub
54                 return null;
55             }
56             
57             public Connection getConnection() throws SQLException {
58                 try {
59                     Class.forName("com.mysql.jdbc.Driver");
60                     String url="jdbc:mysql:///mybatis";
61                     String user="root";
62                     String password="123";
63                     Connection connection = DriverManager.getConnection(url, user, password);
64                     return connection;
65                 } catch (ClassNotFoundException e) {
66                     e.printStackTrace();
67                 }
68                 return null;
69             }
70         };
71         return ds;
72     }
73 }

在第一种时，写了一个xml的SQL映射文件（EmployeeMapperXml.xml），现在既然不用xml了，就需要另一种你方式来映射SQL吧，mybatis提供面向接口编程的方式。官方文档中是这样说的：

它们的映射的语句可以不需要用 XML 来做，取而代之的是可以使用 Java 注解。比如：
package org.mybatis.example;
public interface BlogMapper {
  @Select("SELECT * FROM blog WHERE id = #{id}")
  Blog selectBlog(int id);
}

我这里写一接口：

EmployeeMapper.java：

package yyc.mybatis.mapper;
import org.apache.ibatis.annotations.Select;
import yyc.mybatis.bean.Employee;
public interface EmployeeMapper {

    @Select("SELECT id,last_name lastName,gender,email FROM tb1_employee WHERE id= #{id}")
    public Employee selectOne(Integer id);
}

测试方法（不用xml来得到SqlSessionFactory的方式也不一样）：

@Test
    public void testJavaConfig(){
        DataSource dataSource = EmployeeDataSourceFactory.getEmployeeDataSorce();
        TransactionFactory transactionFactory = new JdbcTransactionFactory();
        Environment environment = new Environment("development", transactionFactory, dataSource);
        Configuration configuration = new Configuration(environment);
        configuration.addMapper(EmployeeMapper.class);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);
    
        
        //2.获取sqlSession实例，能直接执行已经映射的sql语句
                SqlSession openSession = sqlSessionFactory.openSession();
                
                try {
                    EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
                    Employee employee = mapper.selectOne(3);
                    System.out.println(employee);
                } catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }finally {
                    openSession.close();
                }
    }

输出：

Employee [id=3, lastName=mac, gender=1, [email protected]]

这样就完全脱离了两个xml配置文件实现查询数据库。