以前用过一次ibatis2.x, 最近看到它改名了,并且已经升级到3.0.2, 就下载来尝试了下,下面简单说下, 希望能给想尝试不同ORM框架的朋友一些借鉴，我使用的是MySQL 5.1.x数据库。
首先, mybatis也有generator, 叫abator, 需要自己从svn上checkout出来:
svn co http://mybatis.googlecode.com/svn/sub-projects/generator/trunk/ abator
然后我是在eclipse里面使用的, 使用方法见eclipse的帮助文档，不过我再试用此工具时，生成的代码(DAO部分)还是2.x版本的，所以还要继续等官方升级呀。
首先建立包结构，mybatis 3.x文档上有建议的目录结构：
com.test.data 存放Mapper接口和XML，主配置文件
com.test.model 存放表映射实体类
com.test.service 是数据库操作类
mybatis 官方网站 www.mybatis.org
MySQL官方网站 www.mysql.com
需要用到的jar包: mybatis-3.0.1.jar和mysql-connector-java-5.1.10-bin.jar，其他可选包见mybatis发布包内optional目录
MySQL数据表test的 ddl :
CREATE TABLE test (
id int(11) NOT NULL AUTO_INCREMENT,
txt1 varchar(100) CHARACTER SET utf8 DEFAULT NULL,
txt2 varchar(100) CHARACTER SET utf8 DEFAULT NULL,
PRIMARY KEY (id)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
先来看主配置文件src/com/test/data/SqlMapConfig.xml内容：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//ibatis.apache.org//DTD Config 3.0//EN"
"http://ibatis.apache.org/dtd/ibatis-3-config.dtd">
<configuration>
<properties resource="mysql.properties" />
<!-- 别名 -->
<typeAliases>
<typeAlias type="com.test.model.Test" alias="Test" />
</typeAliases>
<!-- 数据库连接配置 -->
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${driver}" />
<property name="url" value="${test.url}" />
<property name="username" value="${test.user}" />
<property name="password" value="${test.pass}" />
</dataSource>
</environment>
</environments>
<!-- 映射文件配置 -->
<mappers>
<mapper resource="com/test/data/TestMapper.xml" />
</mappers>
</configuration>
上面配置文件种引用了数据库配置属性文件src/mysql.properties，内容如下：
####################################
# Database Connectivity Properties
####################################
driver=com.mysql.jdbc.Driver
# test
test.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&connectionCollation=utf8_general_ci
test.user=aa
test.pass=1234
下面是数据库实体类 src/com/test/model/Test.java，内容如下：
package com.test.model;
public class Test implements java.io.Serializable {
/**
* serialVersionUID
*/
private static final long serialVersionUID = -4081457458619235448L;
private int id;
private String txt1;
private String txt2;
public void setId(int id) {
this.id = id;
}
public int getId() {
return this.id;
}
public void setTxt1(String txt) {
this.txt1 = txt;
}
public String getTxt1() {
return this.txt1;
}
public void setTxt2(String txt) {
this.txt2 = txt;
}
public String getTxt2() {
return this.txt2;
}
}
然后是对应的Mapper接口和XML文件，先看Mapper.xml文件 src/com/test/data/TestMapper.xml，注意，在该Mapper配置文件中，我并没有写resultMap属性，是因为我使用了#{属性名}方式，mybatis会自动去匹配实体类Test.java和字段之间的对应。
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"
"http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
<mapper namespace="com.test.data.TestMapper">
<select id="selectByid" parameterType="int" resultType="Test">
SELECT * FROM test WHERE id =#{id}
</select>
<select id="selectByPage" resultType="Test">
SELECT * FROM test ORDER BY id
</select>
<insert id="insertTest" parameterType="Test">
INSERT INTO test (txt1,txt2)
VALUES(#{txt1},#{txt2})
</insert>
<update id="updateTest" parameterType="Test">
UPDATE test SET txt1=#{txt1},txt2=#{txt2} WHERE id=#{id}
</update>
<delete id="deleteTestByid" parameterType="int">
DELETE FROM test WHERE id=#{id}
</delete>
</mapper>
下面是Mapper接口，为了方便进行单元测试和类型安全，新版mybatis建议使用接口来定义上面数据库的操作：src/com/test/data/TestMapper.java
package com.test.data;
import java.util.List;
import com.test.model.Test;
public interface TestMapper {
Test selectByid(int id);
List<Test> selectByPage();
void insertTest(Test test);
void updateTest(Test test);
void deleteTestByid(int id);
}
然后是session工厂：src/com/test/service/MyFactory.java
package com.test.service;
import java.io.IOException;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
public class MyFactory {
private static SqlSessionFactory sqlSessionFactory = null;
static {
String resource = "com/test/data/SqlMapConfig.xml";
Reader reader = null;
try {
reader = Resources.getResourceAsReader(resource);
} catch (IOException e) {
System.err.println(e);
}
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
}
public static SqlSessionFactory sessionFactory() {
return sqlSessionFactory;
}
}
操作类 src/com/test/service/TestService.java
package com.test.service;
import java.util.List;
import org.apache.ibatis.session.RowBounds;
import org.apache.ibatis.session.SqlSession;
import com.test.data.TestMapper;
import com.test.model.Test;
import com.test.service.MyFactory;
public class TestService {
private static TestService instance = null;
private TestService() {
}
public static TestService getInstance() {
if (instance == null) {
instance = new TestService();
}
return instance;
}
/**
* select测试
*
* @param id
* @return
*/
public Test selectOneByid(int id) {
Test t = null;
SqlSession session = MyFactory.sessionFactory().openSession();
try {
TestMapper mapper = session.getMapper(TestMapper.class);
t = mapper.selectByid(id);
} finally {
if (session != null)
session.close();
}
return t;
}
/**
* select翻页测试
*
* @param pg
* @param pz
* @return
*/
@SuppressWarnings("unchecked")
public List<Test> listByPage(int pg, int pz) {
List<Test> tests = null;
// 处理分页
int offset = 0;
int limit = 0;
if (pg > 0)
offset = (pg - 1) * pz;
else
offset = 0;
limit = pz;
SqlSession session = MyFactory.sessionFactory().openSession();
try {
String mapper = "com.test.data.TestMapper.selectByPage";
// 分页处理，这里的分页是采用JDBC方式，对于数据量大的数据库，会有com.mysql.jdbc.PacketTooBigException错误，下面我会改进一下
RowBounds rowBounds = new RowBounds(offset, limit);
tests = session.selectList(mapper, null, rowBounds);
} finally {
if (session != null)
session.close();
}
return tests;
}
/**
* insert测试
*
* @param t
* @return
*/
public int insertOne(Test t) {
int ret = 0;
SqlSession session = MyFactory.sessionFactory().openSession();
try {
TestMapper mapper = session.getMapper(TestMapper.class);
mapper.insertTest(t);
session.commit();
ret = 1;
} finally {
if (session != null)
session.close();
}
return ret;
}
/**
* update测试
*
* @param t
* @return
*/
public int updateOne(Test t) {
int ret = 0;
SqlSession session = MyFactory.sessionFactory().openSession();
try {
TestMapper mapper = session.getMapper(TestMapper.class);
mapper.updateTest(t);
session.commit();
ret = 1;
} finally {
if (session != null)
session.close();
}
return ret;
}
/**
* delete测试
*
* @param id
* @return
*/
public int deleteOneByid(int id) {
int ret = 0;
SqlSession session = MyFactory.sessionFactory().openSession();
try {
TestMapper mapper = session.getMapper(TestMapper.class);
mapper.deleteTestByid(id);
session.commit();
ret = 1;
} finally {
if (session != null)
session.close();
}
return ret;
}
}
下面就来看下具体如何使用： src/MyTest.java
import java.util.Iterator;
import java.util.List;
import com.test.model.Test;
import com.test.service.TestService;
public class MyTest {
/**
* @param args
*/
public static void main(String[] args) {
// select测试
int id = 23;
Test test = TestService.getInstance().selectOneByid(id);
System.out.println(test.getId() + "," + test.getTxt1() + ","
+ test.getTxt2());
// select分页测试
List<Test> tests = null;
int pg = 1;// 我的数据库预置了100多万条记录，当pg比较大时，会抛出com.mysql.jdbc.PacketTooBigException错误，也就是说mybatis把前面所有数据都取出来，然后再分页，儿不是利用MySQL数据库特有的分页机制limit ?,?
int pz = 10;// 每页取10条
tests = TestService.getInstance().listByPage(pg, pz);
if (tests != null) {
Iterator<Test> it = tests.iterator();
while (it.hasNext()) {
Test t = it.next();
System.out.println(t.getId() + "," + t.getTxt1() + ","
+ t.getTxt2());
}
} else {
System.err.println("没有数据");
}
// insert测试
Test t1 = new Test();
t1.setTxt1("hello1");
t1.setTxt2("hello2");
int ret = TestService.getInstance().insertOne(t1);
System.out.println("写入 " + ret + " 条记录");
// update测试
Test t2 = new Test();
t2.setId(23423);
t2.setTxt1("hello3");
t2.setTxt2("hello4");
ret = TestService.getInstance().updateOne(t1);
System.out.println("更新 " + ret + " 条记录");
// delete测试
id = 2324;
ret = TestService.getInstance().deleteOneByid(id);
System.out.println("删除 " + ret + " 条记录");
}
}
改进分页方式，我们利用MySQL独特的limit ?,?方式进行分页，这是效率最高的方式，有人说这么改会造成数据库移植的麻烦，但是进行移植(比如移植到Oracle)时很多SQL本身都要修改，所以这种麻烦微不足道，下面给出修改后的代码：
修改 src/com/test/data/TestMapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"
"http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
<mapper namespace="com.test.data.TestMapper">
<select id="selectByid" parameterType="int" resultType="Test">
SELECT * FROM test WHERE id =#{id}
</select>
<select id="selectByPage" resultType="Test">
SELECT * FROM test ORDER BY id LIMIT #{offset},#{limit} <!--这里修改了-->
</select>
<insert id="insertTest" parameterType="Test">
INSERT INTO test (txt1,txt2)
VALUES(#{txt1},#{txt2})
</insert>
<update id="updateTest" parameterType="Test">
UPDATE test SET txt1=#{txt1},txt2=#{txt2} WHERE id=#{id}
</update>
<delete id="deleteTestByid" parameterType="int">
DELETE FROM test WHERE id=#{id}
</delete>
</mapper>
相应Mapper接口也要修改：src/com/test/data/TestMapper.java
package com.test.data;
import java.util.List;
import org.apache.ibatis.annotations.Param;
import com.test.model.Test;
public interface TestMapper {
Test selectByid(int id);
List<Test> selectByPage(@Param("offset") int offset, @Param("limit") int limit); //这里修改了，使用了mybatis 3.x提供的注解的方法
void insertTest(Test test);
void updateTest(Test test);
void deleteTestByid(int id);
}
相应操作类修改：src/com/test/service/TestService.java
package com.test.service;
import java.util.List;
import org.apache.ibatis.session.SqlSession;
import com.test.data.TestMapper;
import com.test.model.Test;
import com.test.service.MyFactory;
public class TestService {
private static TestService instance = null;
private TestService() {
}
public static TestService getInstance() {
if (instance == null) {
instance = new TestService();
}
return instance;
}
/**
* select测试
*
* @param id
* @return
*/
public Test selectOneByid(int id) {
Test t = null;
SqlSession session = MyFactory.sessionFactory().openSession();
try {
TestMapper mapper = session.getMapper(TestMapper.class);
t = mapper.selectByid(id);
} finally {
if (session != null)
session.close();
}
return t;
}
/**
* select翻页测试
*
* @param pg
* @param pz
* @return
*/
public List<Test> listByPage(int pg, int pz) {
List<Test> tests = null;
// 处理分页
int offset = 0;
int limit = 0;
if (pg > 0)
offset = (pg - 1) * pz;
else
offset = 0;
limit = pz;
SqlSession session = MyFactory.sessionFactory().openSession();
try {
TestMapper mapper = session.getMapper(TestMapper.class); // 这里修改了，放弃RowBounds方式
tests = mapper.selectByPage(offset, limit);
} finally {
if (session != null)
session.close();
}
return tests;
}
/**
* insert测试
*
* @param t
* @return
*/
public int insertOne(Test t) {
int ret = 0;
SqlSession session = MyFactory.sessionFactory().openSession();
try {
TestMapper mapper = session.getMapper(TestMapper.class);
mapper.insertTest(t);
session.commit();
ret = 1;
} finally {
if (session != null)
session.close();
}
return ret;
}
/**
* update测试
*
* @param t
* @return
*/
public int updateOne(Test t) {
int ret = 0;
SqlSession session = MyFactory.sessionFactory().openSession();
try {
TestMapper mapper = session.getMapper(TestMapper.class);
mapper.updateTest(t);
session.commit();
ret = 1;
} finally {
if (session != null)
session.close();
}
return ret;
}
/**
* delete测试
*
* @param id
* @return
*/
public int deleteOneByid(int id) {
int ret = 0;
SqlSession session = MyFactory.sessionFactory().openSession();
try {
TestMapper mapper = session.getMapper(TestMapper.class);
mapper.deleteTestByid(id);
session.commit();
ret = 1;
} finally {
if (session != null)
session.close();
}
return ret;
}
}
好了，src/MyTest.java不用做修改，再次运行吧。
总结：mybatis 3.0.2 是个轻量级ORM框架，优点是使用简单，直接使用SQL来交互，占用内存少，速度比较快， 缺点是分页处理采用JDBC自身的方式，效率低，另外，数据库间移植不方便，需要修改SQL，再就是没有类似hibernate的代码生成工具。
以上是个人观点，没有任何权威性，希望各位看过的朋友批评指正。