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一、前言
MyBatis通用Mapper3是对mybaits的数据库操作的一层封装，之前使用时候是根据数据库表生成mapper.xml，mapper的接口类，这个mapper.xml和接口类被代理后生成能够操作数据对应表的基础功能，而Mapper3则是对其封装，基础功能不在需要mapper.xml，接口类只需要继承封装好的Mapper
二、如何使用
2.1 引入maven配置
SpringBoot应用只需要引入：
org.mybatis.spring.boot
mybatis-spring-boot-starter
1.1.1
tk.mybatis
mapper-spring-boot-starter
1.1.0
com.github.pagehelper
pagehelper-spring-boot-starter
1.1.0
2.2 generator 生成基础文件
在src/main/resources下面
generator.xml文件
//属性值，下面的config.properties文件
//数据源
//Do生成
cofing.properties文件
jdbc.driverClass = com.mysql.jdbc.Driver
jdbc.url = jdbc:mysql://1270.0.1:3308/db
jdbc.user = ****
jdbc.password =****
jdbc.maxPoolSize=50
jdbc.minPoolSize=10
jdbc.maxStatements=100
jdbc.testConnection=true
# 插件
mapper.plugin = tk.mybatis.mapper.generator.MapperPlugin
mapper.Mapper = tk.mybatis.mapper.common.Mapper
然后在pom.xml配置如下：
${basedir}/src/main/java
com.zlx.demo.web.speech.mapper
com.zlx.alin.demo.speech.model
${basedir}/src/main/resources
mapper
3.4.2
3.4.1.snapshot
5.1.30
1.2.4
org.mybatis.generator
mybatis-generator-maven-plugin
1.3.2
${basedir}/src/main/resources/generator/generatorConfig.xml
true
true
mysql
mysql-connector-java
${mysql.version}
tk.mybatis
mapper
${mapper.version}
然后在pom所在目录执行：mvn mybatis-generator:generate 即可
生成的Mapper接口文件：
public interface SwardManMapper extends Mapper{
}
生成的Mapper.xml文件（里面没有任何操作）：
生成的Do文件：
@Table(name="lassen_swardman")
public class SwardManDo {
@Id
@Column(name = "id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private Integer guild_id;
private String creator;
private String modifier;
private String name;
private String status;
private Date gmt_create;
private Date gmt_modified;
private String is_deleted;
private Integer power;
public String getCreator() {
return creator;
}
public void setCreator(String creator) {
this.creator = creator;
}
public String getModifier() {
return modifier;
}
public void setModifier(String modifier) {
this.modifier = modifier;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
public Date getGmt_create() {
return gmt_create;
}
public void setGmt_create(Date gmt_create) {
this.gmt_create = gmt_create;
}
public Date getGmt_modified() {
return gmt_modified;
}
public void setGmt_modified(Date gmt_modified) {
this.gmt_modified = gmt_modified;
}
public String getIs_deleted() {
return is_deleted;
}
public void setIs_deleted(String is_deleted) {
this.is_deleted = is_deleted;
}
public Integer getPower() {
return power;
}
public void setPower(Integer power) {
this.power = power;
}
public Integer getGuild_id() {
return guild_id;
}
public void setGuild_id(int guild_id) {
this.guild_id = guild_id;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
}
2.3 测试
@RestController
@RequestMapping(value = "/speech/test")
public class TestRpc {
@Autowired
SwardManMapper swardManMapper;
@RequestMapping(value = "selectAll", method = { RequestMethod.GET, RequestMethod.POST })
public DecorateActionResult selectAll() {
ActionResult result = new ActionResult();
DecorateActionResult resultNew = new DecorateActionResult();
resultNew.setContent(result);
try {
result.setRetValue(swardManMapper.selectAll());
} catch (Exception ee) {
result.setErrorMessage(ee.getLocalizedMessage());
resultNew.setHasError(true);
}
return resultNew;
}
}
三、原理分析
一切的不同在于mapper接口类继承了Mapper
public interface Mapper extends
BaseMapper,
ExampleMapper,
RowBoundsMapper,
Marker {
}
public interface BaseMapper extends
BaseSelectMapper,
BaseInsertMapper,
BaseUpdateMapper,
BaseDeleteMapper {
}
public interface BaseSelectMapper extends
SelectOneMapper,
SelectMapper,
SelectAllMapper,
SelectCountMapper,
SelectByPrimaryKeyMapper,
ExistsWithPrimaryKeyMapper {
}
public interface SelectAllMapper {
/**
* 查询全部结果
*
* @return
*/
@SelectProvider(type = BaseSelectProvider.class, method = "dynamicSQL")
List selectAll();
}
一层层继承后找到了上面调用的selectAll的定义，原来使用的是SelectProvider注解，再看下selectAll的实现类BaseSelectProvider
public class BaseSelectProvider extends MapperTemplate {
public BaseSelectProvider(Class mapperClass, MapperHelper mapperHelper) {
super(mapperClass, mapperHelper);
}
...........
/**
* 查询
*
* @param ms
* @return
*/
public String selectOne(MappedStatement ms) {
Class entityClass = getEntityClass(ms);
//修改返回值类型为实体类型
setResultType(ms, entityClass);
StringBuilder sql = new StringBuilder();
sql.append(SqlHelper.selectAllColumns(entityClass));
sql.append(SqlHelper.fromTable(entityClass, tableName(entityClass)));
sql.append(SqlHelper.whereAllIfColumns(entityClass, isNotEmpty()));
return sql.toString();
}
/**
* 查询全部结果
*
* @param ms
* @return
*/
public String selectAll(MappedStatement ms) {
final Class entityClass = getEntityClass(ms);
//修改返回值类型为实体类型
setResultType(ms, entityClass);
StringBuilder sql = new StringBuilder();
sql.append(SqlHelper.selectAllColumns(entityClass));
sql.append(SqlHelper.fromTable(entityClass, tableName(entityClass)));
sql.append(SqlHelper.orderByDefault(entityClass));
return sql.toString();
}
}
至此大概知道了是怎么玩的了，这些函数里面是拼接sql语句的。所以如果需要我们可以重写这些SelectProvider实现自己的逻辑，比如查找时候之筛选is_deleted='n'的等等。
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