发表于： 2019-11-14 02:03:55
4 746
一、今天完成的事情
*完成MyBatis的代码运行：
1. 创建maven项目，项目整体框架如下
2. 添加依赖
3. 编写Student.java类，描述实体，包含若干个实体的属性
package pojo;
public class Student {
private int id;
private String name;
private String create_at;
private String update_at;
public Student(){
}
public Student(int id, String name, String create_at, String update_at) {
this.id = id;
this.name = name;
this.create_at = create_at;
this.update_at = update_at;
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getCreate_at() {
return create_at;
}
public void setCreate_at(String create_at) {
this.create_at = create_at;
}
public String getUpdate_at() {
return update_at;
}
public void setUpdate_at(String update_at) {
this.update_at = update_at;
}
@Override
public String toString() {
return "Student{" + "ID=" + id + ", Name='" + name + "'" +
", Created at=" + create_at + ", Updated at=" + update_at+"}";
}
}
4. 编写StudentMapper.java接口，体现实体在数据库的行为，对实体行为进行描述
package mapper;
import pojo.Student;
public interface StudentMapper {
void insertStudent(Student student);
Student queryById(int id);
void updateStudent(int id);
}
5. 编写Student.xml，这是实体行为在数据库操作上的具体实现，包含了sql代码和映射定义信息
<?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="mapper.StudentMapper">
<insert id="insertStudent" parameterType="pojo.Student">
INSERT INTO STUDENT(ID,NAME,CREATE_AT,UPDATE_AT) VALUES(#{id},#{name},#{create_at},#{update_at})
</insert>
<select id="queryById" parameterType="int" resultType="pojo.Student">
SELECT * FROM STUDENT WHERE ID=#{ID}
</select>
<update id="updateStudent">
UPDATE STUDENT SET NAME=#{name},CREATE_AT=#{create_at},UPDATE_AT=#{update_at} WHERE ID=#{id}
</update>
</mapper>
6. 编写mybatis-config.xml，包含数据库连接配置、Student类的mapper映射器
<?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>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver”/> //第一遍时没加cj报错
<property name="url" value="jdbc:mysql://localhost:3306/entryform"/>
<property name="username" value="root"/>
<property name="password" value="rootpass"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="mapper/Student.xml"/>
</mappers>
</configuration>
7. 测试
//import javax.annotation.Resources;
import java.io.IOException;
import java.io.InputStream;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import mapper.StudentMapper;
import pojo.Student;
import org.apache.ibatis.io.Resources;
public class Test {
@org.junit.Test
public void testInsertStudent() throws IOException {
//get mybatis-config.xml
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
Student student = new Student();
//student.setId(2);
student.setName("rueben");
student.setCreate_at("20191113");
student.setUpdate_at("20191113");
studentMapper.insertStudent(student);
sqlSession.commit();
} finally {
sqlSession.close();
}
}
@org.junit.Test
public void testQueryById() throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
Student student = studentMapper.queryById(1);
System.out.println(student);
} finally {
sqlSession.close();
}
}
}
二、遇到的问题
1.第一遍运行的时候getResourceAsStream报错，cannot resolve method，折腾了半天，最后发现Resource这个类不止一个定义，当引入包javax.annotation.Resources;时，Resources并不提供getResourceAsStream这个方法，只有当引入包org.apache.ibatis.io.Resources时，才有这个方法。
2.
这个虽然不知道原因但是跟着改就行了。- 3.第一遍运行的时候querytest通过了，inserttest没有通过，报错太多懒得看，自己想了想，可能是因为已经在数据库里把id设为自增类，但是实体类student.java里给id写了setter和getter，会不会是这个问题，把setter删掉之后运行通过。
- 4.create_at和update_at这两天为了偷懒直接改成String类型然后手动赋值了，这个后面再改吧～
三、明天的计划
1. 把create和update以及其他fields补上
2. 总结jdbctemplate和mybatis的区别
3. 玩云服务器
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