Mybatis抽取基类BaseMapper增删改查的实现

目前项目当中使用mapper.xml文件方式对数据库进行操作,但是每个里边都有增/删/改/查,为了方便开发,把这些公共的代码提取出来,不用当做基类,不用每个Mapper文件都写了

准备工作:

1:数据库表

CREATE TABLE `t_permission` (
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '权限ID',
  `type` int(11) NOT NULL COMMENT '权限类型',
  `name` varchar(255) NOT NULL COMMENT '权限名称',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=24 DEFAULT CHARSET=utf8 COMMENT='权限表';

2:准备实体类

public class TPermissionEntity {

	@PrimaryKey //下面步骤2中自定义注解
	private Integer id;//权限ID
	
	private Integer type;//权限类型
	private String name;//权限名称
	
	//省略了get,set方法....
	
}

步骤1:编写工具类Tools:作用:用于驼峰和数据库字段的转换

因为类的名称用的是驼峰命名,所以这里需要转换一下

import java.util.regex.Matcher;
import java.util.regex.Pattern;
/*
* 驼峰名称和下划线名称的相互转换
*/
public class Tool {
	
	private static Pattern linePattern = Pattern.compile("_(\\w)");
	/** 下划线转驼峰 */
	public static String lineToHump(String str) {
		str = str.toLowerCase();
		Matcher matcher = linePattern.matcher(str);
		StringBuffer sb = new StringBuffer();
		while (matcher.find()) {
			matcher.appendReplacement(sb, matcher.group(1).toUpperCase());
		}
		matcher.appendTail(sb);
		return sb.toString();
	}

	private static Pattern humpPattern = Pattern.compile("[A-Z]");
	/** 驼峰转下划线,效率比上面高 */
	public static String humpToLine(String str) {
		Matcher matcher = humpPattern.matcher(str);
		StringBuffer sb = new StringBuffer();
		while (matcher.find()) {
			matcher.appendReplacement(sb, "_" + matcher.group(0).toLowerCase());
		}
		matcher.appendTail(sb);
		return sb.toString();
	}

}

步骤2:自定义两个注解,分别用于类字段的排除和字义主键

@Target({ElementType.FIELD})  
@Retention(RetentionPolicy.RUNTIME) 
public @interface Exclude {

}
@Target({ElementType.FIELD})  
@Retention(RetentionPolicy.RUNTIME)  
public @interface PrimaryKey {  
    String value() default "";  
}

步骤3:自定义动态sql生成类BaseSqlProvider<T>

作用:根据传入的对象动态获取表名和字段名生成动态的sql语句,再执行

@Insert,@Select,@update,@Delete是直接配置SQL语句,而@InsertProvider,@UpdateProvider,@SelectProvider,@DeleteProvider则是通过SQL工厂类及对应的方法生产SQL语句

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;
import org.apache.ibatis.annotations.Options;
import org.apache.ibatis.jdbc.SQL;
import com.example.demo.common.utils.Tool;

public class BaseSqlProvider<T> {

	@Options
	public String add(T bean) {

		SQL sql = new SQL();

		Class clazz = bean.getClass();

		String tableName = clazz.getSimpleName();
		
		String realTableName = Tool.humpToLine(tableName).replaceAll("_entity", "").substring(1);
		sql.INSERT_INTO(realTableName);

		List<Field> fields = getFields(clazz);
		for (Field field : fields) {

			field.setAccessible(true);

			String column = field.getName();

			System.out.println("column:" + Tool.humpToLine(column));

			sql.VALUES(Tool.humpToLine(column), String.format("#{" + column + ",jdbcType=VARCHAR}"));

		}

		return sql.toString();
	}

	public String delete(T bean) {

		SQL sql = new SQL();

		Class clazz = bean.getClass();

		String tableName = clazz.getSimpleName();

		String realTableName = Tool.humpToLine(tableName).replaceAll("_entity", "").substring(1);
		sql.DELETE_FROM(realTableName);

		List<Field> primaryKeyField = getPrimarkKeyFields(clazz);

		if (!primaryKeyField.isEmpty()) {

			for (Field pkField : primaryKeyField) {
				pkField.setAccessible(true);
				sql.WHERE(pkField.getName() + "=" + String.format("#{" + pkField.getName() + "}"));
			}

		} else {

			sql.WHERE(" 1= 2");

			throw new RuntimeException("对象中未包含PrimaryKey属性");
		}

		return sql.toString();
	}

	private List<Field> getPrimarkKeyFields(Class clazz) {

		List<Field> primaryKeyField = new ArrayList<>();
		List<Field> fields = getFields(clazz);
		for (Field field : fields) {
			field.setAccessible(true);
			PrimaryKey key = field.getAnnotation(PrimaryKey.class);
			if (key != null) {
				primaryKeyField.add(field);
			}

		}
		return primaryKeyField;
	}

	private List<Field> getFields(Class clazz) {

		List<Field> fieldList = new ArrayList<>();
		Field[] fields = clazz.getDeclaredFields();
		for (Field field : fields) {
			field.setAccessible(true);
			Exclude key = field.getAnnotation(Exclude.class);
			if (key == null) {
				fieldList.add(field);
			}

		}
		return fieldList;
	}

	public String get(T bean) {

		SQL sql = new SQL();

		Class clazz = bean.getClass();

		String tableName = clazz.getSimpleName();

		String realTableName = Tool.humpToLine(tableName).replaceAll("_entity", "").substring(1);
		sql.SELECT("*").FROM(realTableName);

		List<Field> primaryKeyField = getPrimarkKeyFields(clazz);

		if (!primaryKeyField.isEmpty()) {

			for (Field pkField : primaryKeyField) {
				pkField.setAccessible(true);
				sql.WHERE(pkField.getName() + "=" + String.format("#{" + pkField.getName() + "}"));
				
			}
		} else {

			sql.WHERE(" 1= 2");

			throw new RuntimeException("对象中未包含PrimaryKey属性");
		}
		System.out.println("getSql:"+sql.toString());
		return sql.toString();
	}

	public String update(T bean) {

		SQL sql = new SQL();

		Class clazz = bean.getClass();

		String tableName = clazz.getSimpleName();

		String realTableName = Tool.humpToLine(tableName).replaceAll("_entity", "").substring(1);
		sql.UPDATE(realTableName);

		List<Field> fields = getFields(clazz);
		for (Field field : fields) {

			field.setAccessible(true);

			String column = field.getName();

			if (column.equals("id")) {
				continue;
			}

			System.out.println(Tool.humpToLine(column));

			sql.SET(Tool.humpToLine(column) + "=" + String.format("#{" + column + ",jdbcType=VARCHAR}"));
		}

		List<Field> primaryKeyField = getPrimarkKeyFields(clazz);

		if (!primaryKeyField.isEmpty()) {

			for (Field pkField : primaryKeyField) {
				pkField.setAccessible(true);
				sql.WHERE(pkField.getName() + "=" + String.format("#{" + pkField.getName() + "}"));
			}

		} else {

			sql.WHERE(" 1= 2");

			throw new RuntimeException("对象中未包含PrimaryKey属性");
		}
		System.out.println("updateSql:"+sql.toString());
		return sql.toString();

	}

}

步骤4:编写BaseMapper基类接口

public interface BaseMapper<T> {
	
        //新增一条数据
	@InsertProvider(method = "add",type=BaseSqlProvider.class)
	@Options(useGeneratedKeys=true)
	public int add(T bean);
	
        //根据主键删除一条数据
	@DeleteProvider(method = "delete",type=BaseSqlProvider.class)
	public int delete(T bean);
	
        //根据主键获取一条数据
	@SelectProvider(method = "get",type=BaseSqlProvider.class)
	public T get(T bean);
	
        //修改一条数据
	@UpdateProvider(method = "update",type=BaseSqlProvider.class)
	public int update(T bean);
	
}

说明:@InsertProvider注解中的type指明自定义的SQL工厂类,method是工厂类里对应的方法,方法返回的是对方的sql语句

到这里基类以及它的配置就完成了,接下来,可以使用了

举例:

编写一个TPermissionMapper接口,实现BaseMapper类,并传入一个泛型参数,此时这个TPermissionMapper接口已经具备了,BaseMapper中基本的增/删/改/查功能.同时TPermissionMapper还可以再写自己独有的方法和mapper.xml文件对功能进行扩展

public interface TPermissionMapper extends BaseMapper<TPermissionEntity>{

	//List<TPermissionEntity> queryByPage();

}

在controller当中的应用:

@Controller
public class LoginController {

	@Autowired
	private TPermissionMapper tPermissionMapper;

        //新增
	@ResponseBody
	@RequestMapping(value = "/add")
	public Integer add() {
		TPermissionEntity permissionEntiry = new TPermissionEntity();
		permissionEntiry.setName("test");
		permissionEntiry.setType(3);
		Integer num = tPermissionMapper.add(permissionEntiry);
		return num;
	}
	
        //修改
	@ResponseBody
	@RequestMapping(value = "/update")
	public Integer update() {
		TPermissionEntity permissionEntiry = new TPermissionEntity();
		permissionEntiry.setId(23);
		permissionEntiry.setName("test");
		permissionEntiry.setType(3);
		Integer num = tPermissionMapper.update(permissionEntiry);
		return num;
	}

        //查询
	@ResponseBody
	@RequestMapping(value = "/query")
	public TPermissionEntity query() {
		TPermissionEntity tPermissionEntity = new TPermissionEntity();
		tPermissionEntity.setId(23);
		tPermissionEntity= (TPermissionEntity) tPermissionMapper.get(tPermissionEntity);
		return tPermissionEntity;
	}

        //删除
	@ResponseBody
	@RequestMapping(value = "/delete")
	public Integer delete() {
		TPermissionEntity permissionEntiry = new TPermissionEntity();
		permissionEntiry.setId(22);
		Integer num = tPermissionMapper.delete(permissionEntiry);
		return num;
	}

}

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