mybatis抽取基类BaseMapper增删改查的实现

文章目录[隐藏]

准备工作:
步骤1:编写工具类Tools:作用:用于驼峰和数据库字段的转换
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
步骤3:自定义动态sql生成类BaseSqlProvider<T>
步骤4:编写BaseMapper基类接口

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("#{" + c<span style="color:transparent">本文来源gaodai#ma#com搞*!代#%^码网%</span>olumn + ",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);
 
}

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