快速搭建数据库持久层架构-自动建表,自动装配
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本文使用springboot+mybatis，利用注解和反射技术，帮助正在搭建数据库相关架构的人员快速明白市面上主流类似jpa，hibernate等框架实现原理，使用mybatis来完成框架的自动建表，自动注入，自动映射功能。 1.定义好table注解，将使用数据库驱动编码自动生成表格 @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface Table { String value(); } 2.实体类使用注解，用于数据库table生成,例如: package com.basic.framework.pojo; import com.fasterxml.jackson.annotation.JsonIgnore; import com.smart.mybatis.annotation.Column; import com.smart.mybatis.annotation.Table; import lombok.Getter; import lombok.Setter; @Setter @Getter @Table("tb_admin") public class Admin extends BasePojo { /** * 用户名 */ @Column(value = "username", columnDefinition = "VARCHAR(20)") private String username; /** * 密码 */ @Column(value = "password", columnDefinition = "VARCHAR(60)") @JsonIgnore private String password; /** * 类型 */ @Column(value = "type", columnDefinition = "VARCHAR(20)") private String type; public enum AdminType { superAdmin("超级管理员"), admin("系统管理员"),examAdmin("考试管理员"); private String label; AdminType(String label) { this.label = label; } public String getLabel() { return label; } public void setLabel(String label) { this.label = label; } } } 3.通过反射将实体类中的元素注入到sql中，从而达到自动生成表的目的 public void init(String url, String packageName, String username, String password) { Date begin = new Date(); //获取包下所有class类，获取到后，扫描注解，完成数据库表生成 List classList = getClazzName(packageName, false); for (String className : classList) { String valueName; StringBuilder stringBuilder = new StringBuilder(); try { Object object = Class.forName(className).newInstance(); if (object.getClass().getAnnotation(Table.class) == null) continue; String tableName = object.getClass().getAnnotation(Table.class).value(); if (isTableExist(url, username, password, "SELECT * FROM information_schema.TABLES WHERE TABLE_SCHEMA=(SELECT DATABASE()) AND `table_name` ='" + tableName + "'")) { String excuteAddSql = ""; String excuteModifySql = ""; //表已经存在 List map = findTableFields(url, username, password, "SELECT column_name,column_type,column_default FROM information_schema.columns WHERE `table_name` ='" + tableName + "'"); //遍历属性，如果在结果集中不存在，则需要添加字段 Field[] superFields = object.getClass().getSuperclass().getDeclaredFields(); excuteAddSql += addFiledSql(superFields, map); excuteModifySql += addModifyFiledSql(superFields, map); Field[] fields = object.getClass().getDeclaredFields(); excuteAddSql += addFiledSql(fields, map); excuteModifySql += addModifyFiledSql(fields, map); if (excuteAddSql.length() != 0) { excuteAddSql = excuteAddSql.substring(0, excuteAddSql.length() - 1); excuteAddSql = "ALTER TABLE " + tableName + " ADD " + excuteAddSql; executeSql(excuteAddSql, url, username, password); } if (excuteModifySql.length() != 0) { excuteModifySql = "ALTER TABLE " + tableName + excuteModifySql.substring(0, excuteModifySql.length() - 1); executeSql(excuteModifySql, url, username, password); } continue; } //父类，此时扫描出父类的注解 Field[] superFields = object.getClass().getSuperclass().getDeclaredFields(); for (Field superField : superFields) { if (superField.getAnnotation(GeneratedValue.class) != null) stringBuilder.append(superField.getAnnotation(Id.class).value()).append(" ").append(superField.getAnnotation(Id.class).columnDefinition()).append(" ").append("AUTO_INCREMENT PRIMARY KEY,"); if (superField.getAnnotation(Column.class) != null) stringBuilder.append(superField.getAnnotation(Column.class).value()).append(" ").append(superField.getAnnotation(Column.class).columnDefinition()).append(isNull(superField.getAnnotation(Column.class).isNull())).append(","); } Field[] fields = object.getClass().getDeclaredFields(); for (Field field : fields) { if (field.getAnnotation(Column.class) != null) stringBuilder.append(field.getAnnotation(Column.class).value()).append(" ").append(field.getAnnotation(Column.class).columnDefinition()).append(isNull(field.getAnnotation(Column.class).isNull())).append(","); } valueName = stringBuilder.toString().substring(0, stringBuilder.toString().length() - 1); String executeSql = "CREATE TABLE " + tableName + "(" + valueName + ")"; //表不存在，直接生成 executeSql(executeSql, url, username, password); } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) { e.printStackTrace(); } } Date end = new Date(); System.out.println("====>>init smart table time:" + (end.getTime() - begin.getTime()) + "ms"); } 3.crud框架搭建,本文是在mybatis框架上进行的二次搭建，感兴趣的同学可以省去mybatis，同样使用反射和注解技术，实现底层mysql的crud功能 DAO层: import org.apache.ibatis.annotations.Mapper; import java.util.HashMap; import java.util.List; import java.util.Map; @Mapper public interface BaseMapper { int insertBatch(Map params); int insert(Map params); int update(Map params); int delete(Map params); HashMap findById(Map params); List> list(Map params); HashMap find(Map params); /**count*/ Integer count(Map params); /**批量更新*/ int updateBatch(Map params); } Service层 import com.github.pagehelper.PageInfo; import com.smart.mybatis.page.Pageable; import com.smart.mybatis.pojo.*; import java.util.List; public interface BaseService { int insert(T entity); int insert(List list); int update(T entity); int updateBatch(List entities); int delete(T entity); Object findById(Long id, Class cls); List list(T entity, Class cls); List list(T entity, Class cls, List queryList); List list(T entity, Class cls, List queryList, List groupByList); List list(T entity, Class cls, List orderList, List groupByList, List likes); List list(T entity, Class cls, List queryList, List orderList, List groupByList, List likes); List list(T entity, Class cls, List queryList, List orderList, List groupByList, List likes, List compareList); Object find(T entity); Object find(T entity, List queryList); PageInfo page(Pageable pageable, T entity, Class cls); PageInfo page(Pageable pageable, T entity, Class cls, List orderList, List groupByList, List likes); Integer count(T entity, Class cls, CountField countField); Integer count(T entity, Class cls, CountField countField, List compareList); Integer count(T entity, Class cls, CountField countField, List compareList, List queryList); } BaseServiceImpl层: @Override public int insert(T entity) { Map param = transformObj(entity, TableConstants.INSERT, null, null, null, null, null,null); if (null == param) return 0; int num = baseMapper.insert(param); if (num > 0) { Long keyId = (Long) param.get("id"); addKeyId(entity, keyId); } return num; } @Override public int update(T entity) { return baseMapper.update(transformObj(entity, TableConstants.UPDATE, null, null, null, null, null,null)); } 后面的就不一一列举，实现原理都是一致的，下面我来说说transformObj这个方法: //获取表名 if (null == t.getClass().getAnnotation(Table.class)) return null; Date a = new Date(); Map re = new LinkedHashMap(); re.put(TableConstants.TABLE_NAME, t.getClass().getAnnotation(Table.class).value()); // 拿到该类 Class clz = t.getClass(); // 获取实体类的所有属性，返回Field数组 Field[] fields = clz.getDeclaredFields(); //获取父类id属性 Field[] superFields = clz.getSuperclass().getDeclaredFields(); for (Field field : superFields) { if (null != field.getAnnotation(Id.class) && getFieldValue(t, field) != null) { re.put(TableConstants.KEY_ID, field.getAnnotation(Id.class).value()); re.put(TableConstants.KEY_VALUE, getFieldValue(t, field)); continue; } if (null != field.getAnnotation(Sql.class) && getFieldValue(t, field) != null) re.put("SQL", getFieldValue(t, field)); } if (TableConstants.INSERT.equals(type)) { List keys = new ArrayList();//存放列名 List values = new ArrayList();//存放列值 addParm(superFields, keys, values, t, fields); re.put(TableConstants.COLUMNS, keys); re.put(TableConstants.VALUES, values); } /** * insert添加参数 */ private void addParm(Field[] superFields, List keys, List values, Object t, Field[] fields) { for (Field field : superFields) { if (null != field.getAnnotation(Column.class) && getFieldValue(t, field) != null) { if (null != keys) keys.add(field.getAnnotation(Column.class).value()); if (null != values) values.add(getFieldValue(t, field)); } } for (Field field : fields) { //判断是否存在标签 if (field.getAnnotation(Column.class) != null) { //列不为空 if (null != keys) keys.add(field.getAnnotation(Column.class).value()); if (null != values) values.add(getFieldValue(t, field)); } } } 该方法通过反射获取到实体类的真实值，将真实值保存在map中，通过mapper映射到mapper文件中. SELECT LAST_INSERT_ID() as id INSERT INTO ${TABLE_NAME} ( ${item} ) VALUES ( #{item} ) 如果你想查询，你只需要配置好OneToOne标签将会自动生成链表查询，返回数据通过反射重新注入到实体类。 此处不再一一列举，该框架中还包含了更新，关联查询等等一系列功能，动态注入这些值意味着你不再需要编写费时的xml创建数据库表，自动装配将会帮你生成这些语句，极大的提高了编码效率,具体代码已上传至github，在TestController可以进行体验,后续会继续讲述数据库分布式分库分表，并升级该架构适应分库分表,这是本人第一次写博客，不喜勿喷，大家一起进步。 github地址:sgfh/smart_mybatis （编辑：威海站长网） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |
