准备工作:

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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

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 {

@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 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 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 getPrimarkKeyFields(Class clazz) {

List primaryKeyField = new ArrayList<>();

List 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 getFields(Class clazz) {

List 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 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 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 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 {

//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:无锡看妇科的医院 http://www.ytsg120.cn/

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{

//List 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;

}

名称栏目：mybatis抽取基类BaseMapper
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