加载依赖
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>1.3.1</version>
</dependency>
application 配置(application.yml)
mybatis:
config-location: classpath:mybatis/mybatis-config.xml
mapper-locations: classpath:mybatis/mapper/*.xml
type-aliases-package: com.zhb.entity
spring:
datasource:
driver-class-name: com.mysql.jdbc.Driver
url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8
password: root
username: root
启动类
在启动类中添加对 Mapper 包扫描@MapperScan，Spring Boot 启动的时候会自动加载包路径下的 Mapper。
@Spring BootApplication
@MapperScan("com.zhb.mapper")
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
或者直接在 Mapper 类上面添加注解@Mapper，建议使用上面那种，不然每个 Mapper 加个注解会很麻烦。
代码展示
这里只说下，我们在controller 中 尽量使用 Restful 风格
@RestController
public class UserController {
@Resource
private UserMapper userMapper;
@GetMapping(value = "/users")
public List<UserEntity> getUsers() {
List<UserEntity> users=userMapper.getAll();
return users;
}
@GetMapping(value = "/users/{id}")
public UserEntity getUser(@PathVariable(value = "id") Long id) {
UserEntity user=userMapper.getOne(id);
return user;
}
@PostMapping("/users")
public void save(UserEntity user) {
userMapper.insert(user);
}
@PutMapping("/users")
public void update(UserEntity user) {
userMapper.update(user);
}
@DeleteMapping(value="/users/{id}")
public void delete(@PathVariable("id") Long id) {
userMapper.delete(id);
}
}
实际开发常遇问题
在平常开发中，我们经常会遇到返回树结构，如下展示
[
{
"id": "1",
"name": "山东",
"pid": "0",
"children": [
{
"id": "2",
"name": "济南",
"pid": "1",
"children": [
{
"id": "3",
"name": "高新区",
"pid": "2",
"children": null
}
]
}
]
}
]
(1) java中 通过对list数据进行拼接成树
如下面的方法（这里直接声明了list，往里面添加数据，来演示查询出的list集合）
@GetMapping(value = "/area")
public List<AreaTreeEntity> get(){
List<AreaTreeEntity> res= new ArrayList<>();
Map<String,List<AreaTreeEntity>> childMap = new HashMap<>(16);
//为了方便测试，构建list数据
List<AreaTreeEntity> s = new ArrayList<>();
AreaTreeEntity a = new AreaTreeEntity();
a.setId("1");
a.setName("山东");
a.setPid("0");
s.add(a);
AreaTreeEntity a1 = new AreaTreeEntity();
a1.setId("2");
a1.setName("济南");
a1.setPid("1");
s.add(a1);
AreaTreeEntity a2 = new AreaTreeEntity();
a2.setId("3");
a2.setName("高新区");
a2.setPid("2");
s.add(a2);
for(AreaTreeEntity entity : s){
if ("0".equals(entity.getPid())) {
res.add(entity);
}
else {
List<AreaTreeEntity> childList = (childMap.containsKey(entity.getPid())) ? childMap.get(entity.getPid()) : new ArrayList<>();
childList.add(entity);
if (!childMap.containsKey(entity.getPid())){
childMap.put(entity.getPid(),childList);
}
}
}
for(AreaTreeEntity entity : res){
findChild(entity,childMap);
}
return res;
}
public void findChild(AreaTreeEntity entity,Map<String,List<AreaTreeEntity>> childMap){
if (childMap.containsKey(entity.getId())){
List<AreaTreeEntity> chidList = childMap.get(entity.getId());
for (AreaTreeEntity childEntity : chidList){
findChild(childEntity,childMap);
}
entity.setChildren(chidList);
}
}
经过验证，返回数据如下
[
{
"id": "1",
"name": "山东",
"pid": "0",
"children": [
{
"id": "2",
"name": "济南",
"pid": "1",
"children": [
{
"id": "3",
"name": "高新区",
"pid": "2",
"children": null
}
]
}
]
}
]
(2) 使用mabatis的collection 直接查询出树结构
<mapper namespace="com.zhb.mapper.AreaTreeMapper" >
<resultMap id="TreeResultMap" type="com.zhb.entity.AreaTreeEntity" >
<result column="id" property="id" jdbcType="VARCHAR" />
<result column="name" property="name" jdbcType="VARCHAR" />
<collection property="children" column="id" ofType="com.zhb.entity.AreaTreeEntity" javaType="ArrayList" select="selectChildrenById"/>
</resultMap>
<select id="getAreaTree" resultMap="TreeResultMap">
select id,name from area where parent_id = '0'
</select>
<select id="selectChildrenById" parameterType="java.lang.String" resultMap="TreeResultMap">
select id,name from area where parent_id = #{id}
</select>
</mapper>
完整代码下载：github
注：项目中加入swagger ，方便大家测试，直接访问 http://localhost:8080/swagger-ui.html