Mybatis3使用教程

mybatis 3.0.2 试用小记

转自：http://www.blogjava.net/javaren/archive/2010/09/27/332226.html

 

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 " />


< typeAliases >
< typeAlias type = " com.test.model.Test " alias = " Test " />
typeAliases >


< 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 >


< 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 {

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。

PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"
"http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">



SELECT * FROM test WHERE id =#{id}



SELECT * FROM test ORDER BY id



INSERT INTO test (txt1,txt2)
VALUES(#{txt1},#{txt2})



UPDATE test SET txt1=#{txt1},txt2=#{txt2} WHERE id=#{id}



DELETE FROM test WHERE id=#{id}

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 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;
}


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;
}


@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;
}


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;
}


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;
}


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 {


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}
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;
}


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;
}


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;
}


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;
}


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;
}


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。

 

其它参考地址：

MyBatis google code: http://code.google.com/p/mybatis/

MyBatis运用心得：http://chengjisihan.iteye.com/blog/752168

MyBatis3 SqlSessionFactory ：http://www.cnblogs.com/archie2010/archive/2011/03/02/1968910.html

ibatis教程入门示例： http://quicker.iteye.com/blog/571544

Mybatis,Ibatis,添加,修改,删除,获得结果集:http://javapub.iteye.com/blog/866913