2024-07-12
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In der Java-Entwicklung wird MyBatis als hervorragendes Persistenzschicht-Framework aufgrund seiner einfachen Konfiguration und leistungsstarken Funktionen häufig in verschiedenen Projekten eingesetzt. In diesem Artikel werden die vier Methoden zum Schreiben von SQL in der Mapper-Ebene in MyBatis ausführlich vorgestellt und anhand spezifischer Implementierungscodes am Beispiel der Benutzertabelle ausführlich erläutert.
MyBatis ist ein Semi-ORM-Framework, das SQL in XML-Dateien oder Annotationen abbildet und so Datenbankoperationen vereinfacht. Es unterstützt benutzerdefiniertes SQL, gespeicherte Prozeduren und erweiterte Zuordnungen.
Das Folgende ist ein Beispiel für eine einfache Projektstruktur basierend auf Spring Boot und MyBatis:
springboot-template-mybatis
│ pom.xml
│
├─src
│ └─main
│ ├─java
│ │ └─com
│ │ └─zcs
│ │ │ Application.java
│ │ │
│ │ ├─common
│ │ │ Result.java
│ │ │
│ │ ├─controller
│ │ │ UserControllerByAnnotation.java
│ │ │ UserControllerByMap.java
│ │ │ UserControllerByProvider.java
│ │ │ UserControllerByXml.java
│ │ │
│ │ ├─entity
│ │ │ UserEntity.java
│ │ │
│ │ ├─mapper
│ │ │ │ UserMapperByAnnotation.java
│ │ │ │ UserMapperByMap.java
│ │ │ │ UserMapperByProvider.java
│ │ │ │ UserMapperByXml.java
│ │ │ │
│ │ │ └─provider
│ │ │ UserProvider.java
│ │ │
│ │ └─service
│ │ UserService.java
│ │ UserServiceByMap.java
│ │
│ └─resources
│ │ application.yml
│ │ log4j.properties
│ │
│ └─com
│ └─zcs
│ └─mapper
│ UserMapperByXml.xml
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(50) DEFAULT NULL,
`age` int(11) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci
import lombok.Data;
@Data
public class UserEntity {
private Integer id;
private String name;
private Integer age;
}
import com.zcs.entity.UserEntity;
import org.apache.ibatis.annotations.Mapper;
import java.util.List;
@Mapper
public interface UserMapperByXml {
List<UserEntity> selectAllUsersByXml();
boolean insertUserByXml(UserEntity user);
boolean updateUserByXml(UserEntity user);
boolean deleteUserByXml(Integer id);
}
<?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.zcs.mapper.UserMapperByXml">
<!-- 查询所有用户 -->
<select id="selectAllUsersByXml">
SELECT *
FROM user
</select>
<!-- 插入用户 -->
<insert id="insertUserByXml">
INSERT INTO user (id, name, age)
VALUES (#{id}, #{name}, #{age})
</insert>
<!-- 更新用户 -->
<update id="updateUserByXml">
UPDATE user
SET name = #{name},
age = #{age}
WHERE id = #{id}
</update>
<!-- 删除用户 -->
<delete id="deleteUserByXml">
DELETE
FROM user
WHERE id = #{id}
</delete>
</mapper>
import com.zcs.common.Result;
import com.zcs.entity.UserEntity;
import com.zcs.mapper.UserMapperByXml;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.*;
import javax.annotation.Resource;
import java.util.List;
@Slf4j
@RestController
@RequestMapping("/usersByXml")
public class UserControllerByXml {
@Resource
private UserMapperByXml userMapperByXml;
@GetMapping
public Result<List<UserEntity>> selectAllUsersByAnnotation() {
List<UserEntity> userEntities = userMapperByXml.selectAllUsersByXml();
return Result.success("successfully", userEntities);
}
@PostMapping
public Result<String> insertUserByAnnotation(@RequestBody UserEntity user) {
boolean b = userMapperByXml.insertUserByXml(user);
if (b) {
return Result.success("successfully", "数据插入成功");
}
return Result.error(500, "数据插入失败");
}
@PutMapping
public Result<String> updateUserByAnnotation(@RequestBody UserEntity user) {
boolean b = userMapperByXml.updateUserByXml(user);
if (b) {
return Result.success("successfully", "数据更新成功");
}
return Result.error(500, "数据更新失败");
}
@DeleteMapping
public Result<String> deleteUserByAnnotation(@RequestParam Integer id) {
boolean b = userMapperByXml.deleteUserByXml(id);
if (b) {
return Result.success("successfully", "数据删除成功");
}
return Result.error(500, "数据删除失败");
}
}
import com.zcs.entity.UserEntity;
import org.apache.ibatis.annotations.*;
import java.util.List;
@Mapper
public interface UserMapperByAnnotation {
@Select("SELECT * FROM user")
List<UserEntity> getAllUser();
@Insert("INSERT INTO user (id, name, age) VALUES (#{id}, #{name}, #{age})")
@Options(useGeneratedKeys = true, keyProperty = "id")
boolean insertUser(UserEntity user);
@Update("UPDATE user SET name = #{name}, age = #{age} WHERE id = #{id}")
boolean updateUser(UserEntity user);
@Delete("DELETE FROM user WHERE id = #{id}")
boolean deleteUserById(Integer id);
}
import com.zcs.entity.UserEntity;
import com.zcs.mapper.UserMapperByAnnotation;
import org.springframework.stereotype.Service;
import javax.annotation.Resource;
import java.util.List;
@Service
public class UserServiceByAnnotation {
@Resource
private UserMapperByAnnotation userMapperByAnnotation;
public List<UserEntity> getAllUser() {
return userMapperByAnnotation.getAllUser();
}
public boolean insertUser(UserEntity user) {
return userMapperByAnnotation.insertUser(user);
}
public boolean updateUser(UserEntity user) {
return userMapperByAnnotation.updateUser(user);
}
public boolean deleteUserById(Integer id) {
return userMapperByAnnotation.deleteUserById(id);
}
}
import com.zcs.common.Result;
import com.zcs.entity.UserEntity;
import com.zcs.service.UserServiceByAnnotation;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.*;
import javax.annotation.Resource;
import java.util.List;
@Slf4j
@RestController
@RequestMapping("/usersByAnnotation")
public class UserControllerByAnnotation {
@Resource
private UserServiceByAnnotation userServiceByAnnotation;
@GetMapping
public Result<List<UserEntity>> getAllUser() {
List<UserEntity> allUserM = userServiceByAnnotation.getAllUser();
return Result.success("success", allUserM);
}
@PostMapping
public Result<String> insertUser(@RequestBody UserEntity user) {
boolean b = userServiceByAnnotation.insertUser(user);
if (b) {
return Result.success("success", "数据插入成功");
}
return Result.error(500, "数据插入失败");
}
@PutMapping
public Result<String> updateUser(@RequestBody UserEntity user) {
boolean b = userServiceByAnnotation.updateUser(user);
if (b) {
return Result.success("success", "数据更新成功");
}
return Result.error(500, "数据更新失败");
}
@DeleteMapping
public Result<String> deleteUserById(@RequestParam Integer id) {
boolean b = userServiceByAnnotation.deleteUserById(id);
if (b) {
return Result.success("success", "数据删除成功");
}
return Result.error(500, "数据删除失败");
}
}
import com.zcs.entity.UserEntity;
import org.apache.ibatis.jdbc.SQL;
public class UserProvider {
public String selectAllUser() {
SQL sql = new SQL();
sql.SELECT("*");
sql.FROM("user");
return sql.toString();
}
public String insertUser(UserEntity userEntity) {
SQL sql = new SQL();
sql.INSERT_INTO("user");
if (userEntity.getId() != null) {
sql.VALUES("id", "#{id}");
}
if (userEntity.getName() != null) {
sql.VALUES("name", "#{name}");
}
if (userEntity.getAge() != null) {
sql.VALUES("age", "#{age}");
}
return sql.toString();
}
public String updateUser(UserEntity userEntity) {
SQL sql = new SQL();
sql.UPDATE("user");
if (userEntity.getName() != null) {
sql.SET("name = #{name}");
}
if (userEntity.getAge() != null) {
sql.SET("age = #{age}");
}
sql.WHERE("id = #{id}");
return sql.toString();
}
public String deleteUserById(Integer id) {
SQL sql = new SQL();
sql.DELETE_FROM("user");
sql.WHERE("id = #{id}");
return sql.toString();
}
}
import com.zcs.entity.UserEntity;
import com.zcs.mapper.provider.UserProvider;
import org.apache.ibatis.annotations.*;
import java.util.List;
@Mapper
public interface UserMapperByProvider {
@SelectProvider(type = UserProvider.class, method = "selectAllUser")
List<UserEntity> selectAllUser();
@InsertProvider(type = UserProvider.class, method = "insertUser")
@Options(useGeneratedKeys = true, keyProperty = "id")
boolean insertUser(UserEntity userEntity);
@UpdateProvider(type = UserProvider.class, method = "updateUser")
boolean updateUser(UserEntity userEntity);
@DeleteProvider(type = UserProvider.class, method = "deleteUserById")
boolean deleteUserById(Integer id);
}
import com.zcs.common.Result;
import com.zcs.entity.UserEntity;
import com.zcs.mapper.UserMapperByProvider;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.*;
import javax.annotation.Resource;
import java.util.List;
@Slf4j
@RestController
@RequestMapping("/usersByProvider")
public class UserControllerByProvider {
@Resource
private UserMapperByProvider userMapper;
@GetMapping
public Result<List<UserEntity>> selectAllUsersByAnnotation() {
List<UserEntity> userEntities = userMapper.selectAllUser();
return Result.success("successfully", userEntities);
}
@PostMapping
public Result<String> insertUserByAnnotation(@RequestBody UserEntity user) {
boolean b = userMapper.insertUser(user);
if (b) {
return Result.success("success", "数据插入成功");
}
return Result.error(500, "数据插入失败");
}
@PutMapping
public Result<String> updateUserByAnnotation(@RequestBody UserEntity user) {
boolean b = userMapper.updateUser(user);
if (b) {
return Result.success("success", "数据更新成功");
}
return Result.error(500, "数据更新失败");
}
@DeleteMapping
public Result<String> deleteUserByAnnotation(@RequestParam Integer id) {
boolean b = userMapper.deleteUserById(id);
if (b) {
return Result.success("success", "数据删除成功");
}
return Result.error(500, "数据删除失败");
}
}
import org.apache.ibatis.annotations.*;
import java.util.List;
import java.util.Map;
@Mapper
public interface UserMapperByMap {
@Select("${sql}")
List<Map<String, Object>> getAllUser(Map<String, Object> map);
@Insert("${sql}")
@Options(useGeneratedKeys = true, keyProperty = "id")
boolean insertUser(Map<String, Object> map);
@Update("${sql}")
boolean updateUser(Map<String, Object> map);
@Delete("${sql}")
boolean deleteUserById(Map<String, Object> map);
}
import com.zcs.mapper.UserMapperByMap;
import org.springframework.stereotype.Service;
import javax.annotation.Resource;
import java.util.List;
import java.util.Map;
@Service
public class UserServiceByMap {
@Resource
private UserMapperByMap userMapperByMap;
public List<Map<String, Object>> getAllUser(Map<String, Object> map) {
String sql = "SELECT * FROM user";
map.put("sql", sql);
return userMapperByMap.getAllUser(map);
}
public boolean insertUser(Map<String, Object> map) {
String sql = "INSERT INTO user (id, name, age) VALUES (#{id}, #{name}, #{age})";
map.put("sql", sql);
return userMapperByMap.insertUser(map);
}
public boolean updateUser(Map<String, Object> map) {
String sql = "UPDATE user SET name = #{name}, age = #{age} WHERE id = #{id}";
map.put("sql", sql);
return userMapperByMap.updateUser(map);
}
public boolean deleteUserById(Map<String, Object> map) {
String sql = "DELETE FROM user WHERE id = #{id}";
map.put("sql", sql);
return userMapperByMap.deleteUserById(map);
}
}
import com.zcs.common.Result;
import com.zcs.service.UserServiceByMap;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.*;
import javax.annotation.Resource;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
@Slf4j
@RestController
@RequestMapping("/usersByMap")
public class UserControllerByMap {
@Resource
private UserServiceByMap userServiceByMap;
@GetMapping
public Result<List<Map<String, Object>>> getAllUser() {
HashMap<String, Object> map = new HashMap<>();
List<Map<String, Object>> allUser = userServiceByMap.getAllUser(map);
return Result.success("success", allUser);
}
@PostMapping
public Result<String> insertUser(@RequestBody Map<String, Object> map) {
boolean b = userServiceByMap.insertUser(map);
if (b) {
return Result.success("success", "数据插入成功");
}
return Result.error(500, "数据插入失败");
}
@PutMapping
public Result<String> updateUserM(@RequestBody Map<String, Object> map) {
boolean b = userServiceByMap.updateUser(map);
if (b) {
return Result.success("success", "数据更新成功");
}
return Result.error(500, "数据更新失败");
}
@DeleteMapping
public Result<String> deleteUserByIdM(@RequestParam Map<String, Object> map) {
boolean b = userServiceByMap.deleteUserById(map);
if (b) {
return Result.success("success", "数据删除成功");
}
return Result.error(500, "数据删除失败");
}
}
In diesem Artikel werden die vier Methoden zum Schreiben von SQL in der Mapper-Ebene von MyBatis ausführlich vorgestellt, einschließlich der Verwendung von XML-Dateien, Anmerkungen, der Bereitstellung von Klassen und der Übergabe von SQL als Parameter. Durch den spezifischen Implementierungscode können Leser die Vor- und Nachteile jeder Methode besser verstehen und die geeignete Methode entsprechend den tatsächlichen Anforderungen auswählen.