我正在尝试运行一个简单的 MyBatis 示例，从“trains”表中选择所有行。
问题是查询执行，但它返回一个具有正确数量元素的列表，但填充了空值。直接使用 JDBC PreparedStatement 运行的相同查询工作正常。
也许这是一个配置问题，但我无法弄清楚我做错了什么。
这是代码。提前致谢。
火车.java
package org.example.mybatis.domain;
public class Train implements Serializable
{
private int id;
private String type;
// getters and setters
}
TrainMapper.java
package org.example.mybatis.persistence;
public interface TrainMapper {
List<Train> getAllTrains();
}
火车选择器.java
package org.example.mybatis.test;
public class TrainSelector implements TrainMapper {
private static String resource = "mybatis-config.xml";
private static SqlSessionFactory factory = null;
private SqlSessionFactory getSqlSessionFactory()
{
if (factory == null)
{
try {
InputStream inputStream = Resources.getResourceAsStream(resource);
factory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
return factory;
}
@Override
public List<Train> getAllTrains()
{
List<Train> trains = null;
SqlSession session = getSqlSessionFactory().openSession();
try {
TrainMapper mapper = session.getMapper(TrainMapper.class);
trains = mapper.getAllTrains();
} finally {
session.close();
}
return trains;
}
public static void main(String[] args) {
List<Train> trains = null;
TrainSelector trainSelector = new TrainSelector();
trains = trainSelector.getAllTrains();
System.out.println(trains);
}
}
mybatis-config.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<properties resource="database.properties" />
<typeAliases>
<typeAlias alias="Train" type="org.example.mybatis.domain.Train" />
<!--package name="org.example.mybatis.domain" />-->
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${database.driver}" />
<property name="url" value="${database.url}" />
<property name="username" value="${database.username}" />
<property name="password" value="${database.password}" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="org/example/mybatis/persistence/TrainMapper.xml" />
</mappers>
</configuration>
火车映射器.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="org.example.mybatis.persistence.TrainMapper">
<cache />
<select id="getAllTrains" parameterType="list" resultType="Train">
SELECT *
FROM trains
</select>
</mapper>
JdbcStatementExample.java
package org.example.mybatis.test;
public class JdbcStatementExample {
private static void selectAllTrains() throws SQLException
{
String sql = "SELECT * FROM trains";
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
String url = "jdbc:mysql://localhost/testing";
String user = "test";
String password = "test";
try {
conn = DriverManager.getConnection(url, user, password);
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
String id = rs.getString("train_id");
String type = rs.getString("train_type");
System.out.println("id: " + id);
System.out.println("type: " + type);
}
} catch (SQLException e) {
throw new RuntimeException(e);
} finally {
if (ps != null) {
ps.close();
}
if (conn != null) {
conn.close();
}
}
}
public static void main(String[] args)
{
try {
selectAllTrains();
} catch (SQLException e) {
e.printStackTrace();
}
}
}