初识ibatis

ibatis简介

         阿帕奇开源项目，一个O/RMapping解决方案，最大特点是小巧，上手很快。如果不需要太复杂的功能，一般都可以满足要求。http://ibatis.apache.org

搭建环境

导入相关jar包

         ojdbc6.jar    ibatis-core-3.0-sources.jar

配置文件：

         jdbc连接的属性文件（db.properties文件）

         总配置文件（SqlMapConfig.xml）

         关于每个实体的映射文件（map文件）

使用步骤：

1.新建web工程ibatis，在src下新建包dao，保存处理数据库相关的类。首先创建数据库连接属性文件db.properties,内容如下：

driver=oracle.jdbc.OracleDriver

url=jdbc:oracle:thin:@localhost:1521:Oracle

usr=xxx

pwd=xxx

2.在数据库中创建表student

create table student(id number,name varchar2(20),age number,class varchar2(20));

insert into student values(1,'张三',18,'高一');

insert into student values(2,'张三',19,'高二');

insert into student values(3,'张三',17,'高三');

insert into student values(4,'张三',15,'高一');

insert into student values(5,'张三',17,'高二');

insert into student values(6,'张三',15,'高三');

insert into student values(7,'张三',19,'高一');

insert into student values(8,'张三',15,'高三');

insert into student values(9,'张三',17,'高二');

commit;

3.根据数据库中表字段创建Student实体类；包名为entity

package entity;

 

public class Student {

         private int id;

         private String name;

         private int age;

         private String className;

         public int getId() {

                   return id;

         }

         public void setId(int id) {

                   this.id = id;

         }

         public String getName() {

                   return name;

         }

         public void setName(String name) {

                   this.name = name;

         }

         public int getAge() {

                  return age;

         }

         public void setAge(int age) {

                   this.age = age;

         }

         public String getClassName() {

                   return className;

         }

         public void setClassName(String className) {

                   this.className = className;

         }

         @Override

         public String toString() {

                   return "Student [id=" + id + ", name=" + name + ", age=" + age

                                     + ", className=" + className + "]";

         }

        

}

4.在dao包下自定义异常类DAOException，继承自Exception,实现查询数据库时抛出自定义异常

package dao;

 

public class DAOException extends Exception {

         public DAOException(String message,Throwable couse){

                   super(message, couse);

         }

}

5．在dao包下定义IStudentDAO接口，定义抽象方法

        

package dao;

 

import java.util.List;

 

import entity.Student;

 

public interface IStudentDAO {

         List<Student> findAll() throws DAOException;

}

5.在dao包下，配置Student实体类的映射文件Student.xml

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE sqlMap    

    PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"    

    "http://ibatis.apache.org/dtd/sql-map-2.dtd">

<sqlMap>

         <!-- alias表示type的简写形式 -->

         <typeAlias alias="Student" type="entity.Student"/>

         <!-- id代表了该sql语句，resultClass表示返回值的类型 -->

          <select id="selectAllStudent" resultClass="Student" >

                 select * from student

          </select>

</sqlMap>

6.在src/dao包下配置SqlMapConfig.xml的总配置文件

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE sqlMapConfig PUBLIC "-//ibatis.apache.org//DTD SQL Map Config 2.0//EN" "http://ibatis.apache.org/dtd/sql-map-config-2.dtd">

<sqlMapConfig>

         <!-- 加载数据库属性配置文件db.properties -->

         <properties resource="dao/db.properties"/>

         <!-- type="JDBC" 时事务是自动提交的,如果要控制事务不自动提交,如下的配置 -->

         <transactionManager type="JDBC" commitRequired="false">

                   <dataSource type="SIMPLE">

                            <property name="JDBC.Driver" value="${driver}"/>

                            <property name="JDBC.ConnectionURL" value="${url}"/>

                            <property name="JDBC.Username" value="${usr}"/>

                            <property name="JDBC.Password" value="${pwd}"/>

                   </dataSource>

         </transactionManager>

         <!-- 引入映射实体类的配置文件 -->

         <sqlMap resource="dao/Student.xml"/>

</sqlMapConfig>

7.在dao包下新建实现IStudentDAO的类，StudentDaoImpl

package dao;

 

import java.io.IOException;

import java.io.Reader;

import java.sql.SQLException;

import java.util.List;

 

import com.ibatis.sqlmap.client.SqlMapClient;

 

import entity.Student;

 

 

public class StudentDaoImpl implements IStudentDAO {

        

         private static SqlMapClient sqlMapClient = null;

         private static Reader reader = null;

         static{

                   try {

                            //将xml文件转换为一个字符输入流

                            reader = com.ibatis.common.resources.Resources.getResourceAsReader("dao/sqlMapConfig.xml");

                            //将字符输入流转换为SqlMapClient

                            sqlMapClient = com.ibatis.sqlmap.client.SqlMapClientBuilder.buildSqlMapClient(reader);

                   } catch (IOException e) {

                            e.printStackTrace();

                   }finally{

                            if(reader != null){

                                     try {

                                               reader.close();

                                     } catch (IOException e) {

                                               e.printStackTrace();

                                     }

                            }

                   }

         }

 

         public List<Student> findAll() throws DAOException {

                   List<Student> list = null;

                   try {

                            //此处的selectAllStudent对应的是Student.xml映射文件中的select标签的id值，代表了那条sql语句

                            list = sqlMapClient.queryForList("selectAllStudent");

                   } catch (SQLException e) {

                            e.printStackTrace();

                   }

                   return list;

         }

 

         public static void main(String[] args) throws Exception {

                   IStudentDAO dao = new StudentDaoImpl();

                   System.out.println(dao.findAll());

         }

}

8.测试查看

Student [id=1, name=张三, age=18, className=null]

Student [id=2, name=张三, age=19, className=null]

Student [id=3, name=张三, age=17, className=null]

Student [id=4, name=张三, age=15, className=null]

Student [id=5, name=张三, age=17, className=null]

Student [id=6, name=张三, age=15, className=null]

Student [id=7, name=张三, age=19, className=null]

Student [id=8, name=张三, age=15, className=null]

Student [id=9, name=张三, age=17, className=null]

 

上面实体类Student中的className字段与数据库中的class字段不对应因此查询出的className都是null，修改数据库中的字段名之后就好了。