MyBatis通用Mapper和PageHelper

如果项目中使用到了MyBatis框架,那么使用通用Mapper和PageHelper分页插件将极大的简化我们的操作。通用Mapper可以简化对单表的CRUD操作,PageHelper分页插件可以帮我们自动拼接分页SQL,并且可以使用MyBatis Geneator来自动生成实体类,Mapper接口和Mapper xml代码,非常的方便。插件地址及作者链接https://gitee.com/free

引入依赖

这里使用Spring Boot来构建,可参考Spring-Boot中使用Mybatis.html搭建一个Spring boot + MyBatis的框架,然后在pom中引入:

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<!-- mybatis -->
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>1.3.1</version>
</dependency>
<!-- 通用mapper -->
<dependency>
<groupId>tk.mybatis</groupId>
<artifactId>mapper-spring-boot-starter</artifactId>
<version>1.1.5</version>
</dependency>
<!-- pagehelper 分页插件 -->
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>1.2.3</version>
</dependency>

接着在pom中配置MyBatis Geneator:

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<build>
<plugins>
<plugin>
<groupId>org.mybatis.generator</groupId>
<artifactId>mybatis-generator-maven-plugin</artifactId>
<version>1.3.5</version>
<dependencies>
<dependency>
<!-- 数据库连接驱动 -->
<groupId>com.oracle</groupId>
<artifactId>ojdbc6</artifactId>
<version>6.0</version>
</dependency>
<dependency>
<groupId>tk.mybatis</groupId>
<artifactId>mapper</artifactId>
<version>3.4.0</version>
</dependency>
</dependencies>
<executions>
<execution>
<id>Generate MyBatis Artifacts</id>
<phase>package</phase>
<goals>
<goal>generate</goal>
</goals>
</execution>
</executions>
<configuration>
<!--允许移动生成的文件 -->
<verbose>true</verbose>
<!-- 是否覆盖 -->
<overwrite>true</overwrite>
<!-- 自动生成的配置 -->
<configurationFile>src/main/resources/mybatis-generator.xml</configurationFile>
</configuration>
</plugin>
</plugins>
</build>

src/main/resources/mybatis-generator.xml为生成器的配置,下文会介绍到。

配置插件

在Spring Boot配置文件application.yml中配置MyBatis:

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mybatis:
# type-aliases扫描路径
type-aliases-package: com.springboot.bean
# mapper xml实现扫描路径
mapper-locations: classpath:mapper/*.xml
property:
order: BEFORE

接下来开始配置插件。

配置通用Mapper

在Spring Boot配置文件application.yml中配置通用Mapper:

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#mappers 多个接口时逗号隔开
mapper:
mappers: com.springboot.config.MyMapper
not-empty: false
identity: oracle

关于参数的说明,参考https://gitee.com/free/Mapper/blob/master/wiki/mapper3/2.Integration.md中的可配参数介绍

除此之外,我们需要定义一个MyMapper接口:

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import tk.mybatis.mapper.common.Mapper;
import tk.mybatis.mapper.common.MySqlMapper;

public interface MyMapper<T> extends Mapper<T>, MySqlMapper<T> {

}

值得注意的是,该接口不能被扫描到,应该和自己定义的Mapper分开。自己定义的Mapper都需要继承这个接口。

配置PageHelper

在Spring Boot配置文件application.yml中配置通用配置PageHelper:

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#pagehelper
pagehelper:
helperDialect: oracle
reasonable: true
supportMethodsArguments: true
params: count=countSql

参数相关说明参考https://github.com/pagehelper/Mybatis-PageHelper/blob/master/wikis/zh/HowToUse.md中的分页插件参数介绍

配置Geneator*

在路径src/main/resources/下新建mybatis-generator.xml:

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
"http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration>
<context id="oracle" targetRuntime="MyBatis3Simple" defaultModelType="flat">

<plugin type="tk.mybatis.mapper.generator.MapperPlugin">
<!-- 该配置会使生产的Mapper自动继承MyMapper -->
<property name="mappers" value="com.springboot.config.MyMapper" />
<!-- caseSensitive默认false,当数据库表名区分大小写时,可以将该属性设置为true -->
<property name="caseSensitive" value="false"/>
</plugin>

<!-- 阻止生成自动注释 -->
<commentGenerator>
<property name="javaFileEncoding" value="UTF-8"/>
<property name="suppressDate" value="true"/>
<property name="suppressAllComments" value="true"/>
</commentGenerator>

<!-- 数据库链接地址账号密码 -->
<jdbcConnection
driverClass="oracle.jdbc.driver.OracleDriver"
connectionURL="jdbc:oracle:thin:@localhost:1521:ORCL"
userId="scott"
password="6742530">
</jdbcConnection>

<javaTypeResolver>
<property name="forceBigDecimals" value="false"/>
</javaTypeResolver>

<!-- 生成Model类存放位置 -->
<javaModelGenerator targetPackage="com.springboot.bean" targetProject="src/main/java">
<property name="enableSubPackages" value="true"/>
<property name="trimStrings" value="true"/>
</javaModelGenerator>

<!-- 生成映射文件存放位置 -->
<sqlMapGenerator targetPackage="mapper" targetProject="src/main/resources">
<property name="enableSubPackages" value="true"/>
</sqlMapGenerator>

<!-- 生成Dao类存放位置 -->
<!-- 客户端代码,生成易于使用的针对Model对象和XML配置文件的代码
type="ANNOTATEDMAPPER",生成Java Model 和基于注解的Mapper对象
type="XMLMAPPER",生成SQLMap XML文件和独立的Mapper接口 -->
<javaClientGenerator type="XMLMAPPER" targetPackage="com.springboot.mapper" targetProject="src/main/java">
<property name="enableSubPackages" value="true"/>
</javaClientGenerator>

<!-- 配置需要生成的表 -->
<table tableName="T_USER" domainObjectName="User" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false">
<generatedKey column="id" sqlStatement="oralce" identity="true"/>
</table>
</context>
</generatorConfiguration>

更详细的说明可参考链接:http://blog.csdn.net/isea533/article/details/42102297

代码生成

配置好MyBatis Geneator后,在eclipse中运行命令mybatis-generator:generate

QQ截图20171227095243.png

以下为自动成成的代码:

User:

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@Table(name = "T_USER")
public class User {
@Id
@Column(name = "ID")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

@Column(name = "USERNAME")
private String username;

@Column(name = "PASSWD")
private String passwd;

@Column(name = "CREATE_TIME")
private Date createTime;

@Column(name = "STATUS")
private String status;

...
}

因为这里数据库试用的是Oracle,其没有主键自动自增的功能,这里先将@GeneratedValue(strategy = GenerationType.IDENTITY)去掉,主键的生成下面会介绍到。生成的主键是BigDecimal类型的,我们将其改为Long类型。

UserMapper:

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import com.springboot.bean.User;
import com.springboot.config.MyMapper;

public interface UserMapper extends MyMapper<User> {
}

UserMapper.xml:

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<?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="com.springboot.mapper.UserMapper">
<resultMap id="BaseResultMap" type="com.springboot.bean.User">
<!--
WARNING - @mbg.generated
-->
<id column="ID" jdbcType="DECIMAL" property="id" />
<result column="USERNAME" jdbcType="VARCHAR" property="username" />
<result column="PASSWD" jdbcType="VARCHAR" property="passwd" />
<result column="CREATE_TIME" jdbcType="TIMESTAMP" property="createTime" />
<result column="STATUS" jdbcType="CHAR" property="status" />
</resultMap>
</mapper>

极其方便的说!

Mapper

要让Spring Boot扫描到Mapper接口,需要在Spring Boot入口类中加入@MapperScan("com.springboot.mapper")注解。

为了获取到Oracle 中序列的值,我们定义一个SeqenceMapper接口:

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public interface SeqenceMapper {
@Select("select ${seqName}.nextval from dual")
Long getSequence(@Param("seqName") String seqName);
}

因为这里仅介绍Mapper自带的CRUD方法,所以UserMapper接口中无需定义任何方法。

通用Service

我们可以定义一个通用的Service,在其中定义一些通用的方法:

IService:

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@Service
public interface IService<T> {

Long getSequence(@Param("seqName") String seqName);

List<T> selectAll();

T selectByKey(Object key);

int save(T entity);

int delete(Object key);

int updateAll(T entity);

int updateNotNull(T entity);

List<T> selectByExample(Object example);
}

其实现类BaseService:

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public abstract class BaseService<T> implements IService<T> {

@Autowired
protected Mapper<T> mapper;
@Autowired
protected SeqenceMapper seqenceMapper;

public Mapper<T> getMapper() {
return mapper;
}
@Override
public Long getSequence(@Param("seqName") String seqName){
return seqenceMapper.getSequence(seqName);
}

@Override
public List<T> selectAll() {
//说明:查询所有数据
return mapper.selectAll();
}

@Override
public T selectByKey(Object key) {
//说明:根据主键字段进行查询,方法参数必须包含完整的主键属性,查询条件使用等号
return mapper.selectByPrimaryKey(key);
}

@Override
public int save(T entity) {
//说明:保存一个实体,null的属性也会保存,不会使用数据库默认值
return mapper.insert(entity);
}

@Override
public int delete(Object key) {
//说明:根据主键字段进行删除,方法参数必须包含完整的主键属性
return mapper.deleteByPrimaryKey(key);
}

@Override
public int updateAll(T entity) {
//说明:根据主键更新实体全部字段,null值会被更新
return mapper.updateByPrimaryKey(entity);
}

@Override
public int updateNotNull(T entity) {
//根据主键更新属性不为null的值
return mapper.updateByPrimaryKeySelective(entity);
}

@Override
public List<T> selectByExample(Object example) {
//说明:根据Example条件进行查询
//重点:这个查询支持通过Example类指定查询列,通过selectProperties方法指定查询列
return mapper.selectByExample(example);
}
}

接下来让UserService接口继承IService接口:

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public interface UserService extends IService<User>{

}

其实现类UserServiceImpl:

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@Repository("userService")
public class UserServiceImpl extends BaseService<User> implements UserService{

}

这样即可在UserService中使用BaseService中的通用方法了。

测试

测试插入:

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@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes = Application.class)
public class ApplicationTest {
@Autowired
private UserService userService;

@Test
public void test() throws Exception {
User user = new User();
user.setId(userService.getSequence("seq_user"));
user.setUsername("scott");
user.setPasswd("ac089b11709f9b9e9980e7c497268dfa");
user.setCreateTime(new Date());
user.setStatus("0");
this.userService.save(user);
}
}

运行代码,查看数据库:

QQ截图20171227102024.png

测试查询:

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Example example = new Example(User.class);
example.createCriteria().andCondition("username like '%i%'");
example.setOrderByClause("id desc");
List<User> userList = this.userService.selectByExample(example);
for (User u : userList) {
System.out.println(u.getUsername());
}

List<User> all = this.userService.selectAll();
for (User u : all) {
System.out.println(u.getUsername());
}

User user = new User();
user.setId(1l);
user = this.userService.selectByKey(user);
System.out.println(user.getUsername());

测试删除:

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User user = new User();
user.setId(4l);
this.userService.delete(user);

分页测试,从第二页开始,每页2条数据:

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PageHelper.startPage(2, 2);
List<User> list = userService.selectAll();
PageInfo<User> pageInfo = new PageInfo<User>(list);
List<User> result = pageInfo.getList();
for (User u : result) {
System.out.println(u.getUsername());
}

查看日志打印出的SQL:

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2017-12-28 10:25:14.033 DEBUG 11116 --- [main] c.s.mapper.UserMapper.selectAll          : ==>  Preparing: SELECT * FROM ( SELECT TMP_PAGE.*, ROWNUM ROW_ID FROM (
SELECT ID,USERNAME,PASSWD,CREATE_TIME,STATUS FROM T_USER ) TMP_PAGE WHERE ROWNUM <= ? ) WHERE ROW_ID > ?
2017-12-28 10:25:14.068 DEBUG 11116 --- [main] c.s.mapper.UserMapper.selectAll : ==> Parameters: 4(Integer), 2(Integer)
2017-12-28 10:25:14.073 DEBUG 11116 --- [main] c.s.mapper.UserMapper.selectAll : <== Total: 2

插件已经帮我自动拼接好了。

其他注意事项参考官方说明。源码链接:https://github.com/wuyouzhuguli/Spring-Boot-Demos/tree/master/27.Spring-Boot-Mapper-PageHelper


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