1 实现思路概述#

1.1 从ResultSet说起#

说到ResultSet，有Java开发经验的“小伙伴”自然最熟悉不过了，不过我相信对于大多数人来说也算是“最熟悉的陌生人”。从ResultSet取值操作大家都会，比如：

private static List<Member> select(String sql) {
    List<Member> result = new ArrayList<>();
    Connection con = null;
    PreparedStatement pstm = null;
    ResultSet rs = null;
    try {
        //1. 加载驱动类
        Class.forName("com.mysql.jdbc.Driver");
        //2. 建立连接
        con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/gp-vip-spring-db-demo", "root","123456");
        //3. 创建语句集
        pstm =  con.prepareStatement(sql);
        //4. 执行语句集
        rs = pstm.executeQuery();
        while (rs.next()){
            Member instance = new Member();
            instance.setId(rs.getLong("id"));
            instance.setName(rs.getString("name"));
            instance.setAge(rs.getInt("age"));
            instance.setAddr(rs.getString("addr"));
            result.add(instance);
        }
        //5. 获取结果集
    }catch (Exception e){
        e.printStackTrace();
    }
    //6. 关闭结果集、关闭语句集、关闭连接
    finally {
        try {
            rs.close();
            pstm.close();
            con.close();
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    return result;
}

以上我们在没有使用框架以前的常规操作。随着业务和开发量的增加，在数据持久层这样的重复代码出现频次非常高。因此，我们就想到将非功能性代码和业务代码进行分离。我们首先想到将ResultSet封装数据的代码逻辑分离，增加一个mapperRow()方法，专门处理对结果的封装，代码如下：

private static List<Member> select(String sql) {
    List<Member> result = new ArrayList<>();
    Connection con = null;
    PreparedStatement pstm = null;
    ResultSet rs = null;
    try {
        //1. 加载驱动类
        Class.forName("com.mysql.jdbc.Driver");
        //2. 建立连接
        con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/gp-vip-spring-db-demo", "root","123456");
        //3. 创建语句集
        pstm =  con.prepareStatement(sql);
        //4. 执行语句集
        rs = pstm.executeQuery();
        while (rs.next()){
            Member instance = mapperRow(rs,rs.getRow());
            result.add(instance);
        }
        //5. 获取结果集
    }catch (Exception e){
        e.printStackTrace();
    }
    //6. 关闭结果集、关闭语句集、关闭连接
    finally {
        try {
            rs.close();
            pstm.close();
            con.close();
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    return result;
}

private static Member mapperRow(ResultSet rs, int i) throws Exception {
    Member instance = new Member();
    instance.setId(rs.getLong("id"));
    instance.setName(rs.getString("name"));
    instance.setAge(rs.getInt("age"));
    instance.setAddr(rs.getString("addr"));
    return instance;
}

但在真实的业务场景中，这样的代码逻辑重复率实在太高，上面的改造只能应用Member类，换一个实体类又要重新封装，聪明的程序员肯定不会通过纯体力劳动给每一个实体类写一个mapperRow()方法，一定会想到代码复用方案。我们不妨来做这样一个改造。
先创建Member类：

package com.gupaoedu.vip.orm.demo.entity;

import lombok.Data;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import java.io.Serializable;

@Entity
@Table(name="t_member")
@Data
public class Member implements Serializable {
    @Id private Long id;
    private String name;
    private String addr;
    private Integer age;

    @Override
    public String toString() {
        return "Member{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", addr='" + addr + '\'' +
                ", age=" + age +
                '}';
    }
}

优化JDBC操作：

public static void main(String[] args) {
    Member condition = new Member();
    condition.setName("Tom");
    condition.setAge(19);
    List<?> result =  select(condition);
    System.out.println(Arrays.toString(result.toArray()));
}

private static List<?> select(Object condition) {

    List<Object> result = new ArrayList<>();

    Class<?> entityClass = condition.getClass();

    Connection con = null;
    PreparedStatement pstm = null;
    ResultSet rs = null;
    try {
        //1. 加载驱动类
        Class.forName("com.mysql.jdbc.Driver");
        //2. 建立连接
        con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/gp-vip-spring-db-demo? characterEncoding=UTF-8&rewriteBatchedStatements=true","root","123456");

        //根据类名找属性名
        Map<String,String> columnMapper = new HashMap<String,String>();
        //根据属性名找字段名
        Map<String,String> fieldMapper = new HashMap<String,String>();
        Field[] fields =  entityClass.getDeclaredFields();
        for (Field field : fields) {
            field.setAccessible(true);
            String fieldName = field.getName();
            if(field.isAnnotationPresent(Column.class)){
                Column column = field.getAnnotation(Column.class);
                String columnName = column.name();
                columnMapper.put(columnName,fieldName);
                fieldMapper.put(fieldName,columnName);
            }else {
                //默认就是字段名、属性名一致
                columnMapper.put(fieldName, fieldName);
                fieldMapper.put(fieldName,fieldName);
            }
        }

        //3. 创建语句集
        Table table = entityClass.getAnnotation(Table.class);
        String sql = "select * from " + table.name();

        StringBuffer where = new StringBuffer(" where 1=1 ");
        for (Field field : fields) {
            Object value =field.get(condition);
            if(null != value){
                if(String.class == field.getType()) {
                    where.append(" and " + fieldMapper.get(field.getName()) + " = '" + value + "'");
                }else{
                    where.append(" and " + fieldMapper.get(field.getName()) + " = " + value + "");
                }
                //其他的在这里就不一一列举，后面我们手写ORM框架时会完善
            }
        }
        System.out.println(sql + where.toString());
        pstm =  con.prepareStatement(sql + where.toString());

        //4. 执行语句集
        rs = pstm.executeQuery();

        //元数据？
        //保存了处理真正数值以外的所有附加信息
        int columnCounts = rs.getMetaData().getColumnCount();
        while (rs.next()){
            Object instance = entityClass.newInstance();
            for (int i = 1; i <= columnCounts; i++) {
                //实体类属性名，对应数据库表的字段名
                //可以通过反射机制拿到实体类的所有字段

                //从rs中取得当前这个游标下的类名
                String columnName = rs.getMetaData().getColumnName(i);
                //有可能是私有的
                Field field = entityClass.getDeclaredField(columnMapper.get(columnName));
                field.setAccessible(true);
                field.set(instance,rs.getObject(columnName));
            }

            result.add(instance);

        }

        //5. 获取结果集
    }catch (Exception e){
        e.printStackTrace();
    }
    //6. 关闭结果集、关闭语句集、关闭连接
    finally {
        try {
            rs.close();
            pstm.close();
            con.close();
        }catch (Exception e){
            e.printStackTrace();
        }
    }

    return result;
}

上面巧妙地利用反射机制读取Class信息和Annotation信息，将数据库表中的列和类中的字段进行关联映射并赋值，以减少重复代码。

1.2 为什么需要ORM框架#

通过前面的讲解，我们已经了解ORM框架的基本实现原理。ORM是指对象关系映射（Object Relation Mapping），映射的不只是对象值，还有对象与对象之间的关系，例如一对多、多对多、一对一这样的表关系。现在市面上ORM框架也非常多，有大家所熟知的Hibernate、Spring JDBC、MyBatis、JPA等。在这里做一个简单的总结，如下表所示。

既然市面上有这么多选择，我为什么还要自己写 ORM框架呢？
这得从我的一次空降担任架构师的经验说起。空降面临最大的难题就是如何取得团队“小伙伴们”的信任。当时，团队总共就8人，每个人的水平参差不齐，甚至有些人还没接触过MySQL，诸如Redis等缓存中间件更不用说了。基本只会使用Hibernate的CRUD，而且已经影响到了系统性能。由于工期紧张，没有时间和精力给团队做系统培训，也为了兼顾可控性，于是就产生了自研ORM框架的想法。我做了这样的顶层设计，以降低团队“小伙伴们”的存息成本，顶层接口统一参数、统一返回值，具体如下。

**（1）规定查询方法的接口模型为： **

/**
 * 获取列表
 * @param queryRule 查询条件
 * @return
 */
List<T> select(QueryRule queryRule) throws Exception;

/**
 * 获取分页结果
 * @param queryRule 查询条件
 * @param pageNo 页码
 * @param pageSize 每页条数
 * @return
 */
Page<?> select(QueryRule queryRule,int pageNo,int pageSize) throws Exception;

/**
 * 根据SQL获取列表
 * @param sql SQL语句
 * @param args 参数
 * @return
 */
List<Map<String,Object>> selectBySql(String sql, Object... args) throws Exception;

/**
 * 根据SQL获取分页
 * @param sql SQL语句
 * @param pageNo 页码
 * @param pageSize 每页条数
 * @return
 */
Page<Map<String,Object>> selectBySqlToPage(String sql, Object [] param, int pageNo, int pageSize) throws Exception;

（2）规定删除方法的接口模型为：

/**
 * 删除一条记录
 * @param entity entity中的ID不能为空，如果ID为空，其他条件不能为空，都为空不予执行
 * @return
 */
boolean delete(T entity) throws Exception;

/**
 * 批量删除
 * @param list
 * @return 返回受影响的行数
 * @throws Exception
 */
int deleteAll(List<T> list) throws Exception;

（3）规定插入方法的接口模型为：

/**
 * 插入一条记录并返回插入后的ID
 * @param entity 只要entity不等于null，就执行插入
 * @return
 */
PK insertAndReturnId(T entity) throws Exception;

/**
 * 插入一条记录自增ID
 * @param entity
 * @return
 * @throws Exception
 */
boolean insert(T entity) throws Exception;

/**
 * 批量插入
 * @param list
 * @return 返回受影响的行数
 * @throws Exception
 */
int insertAll(List<T> list) throws Exception;

（4）规定修改方法的接口模型为：

/**
 *  修改一条记录
 * @param entity entity中的ID不能为空，如果ID为空，其他条件不能为空，都为空不予执行
 * @return
 * @throws Exception
 */
boolean update(T entity) throws Exception;

利用这套基础的API，后面我又基于Redis、MongoDB、ElasticSearch、Hive、HBase各封装了一套，以此来降低团队的学习成本，也大大提升了程序的可控性，更方便统一监控。

2 搭建基础架构#

2.1 Page#

定义Page类的主要目的是为后面的分页查询统一返回结果做顶层支持，其主要功能包括分页逻辑的封装、分页数据。

package javax.core.common;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

/**
 * 分页对象，包含当前页数据及分页信息，如总记录数
 * 能够支持和JQuery EasyUI直接对接，能够支持和BootStrap Table直接对接
 */
public class Page<T> implements Serializable {

   private static final long serialVersionUID = 1L;
   private static final int DEFAULT_PAGE_SIZE = 20;

   private int pageSize = DEFAULT_PAGE_SIZE; //每页的记录数

   private long start; //当前页第一条数据在List中的位置，从0开始

   private List<T> rows; //当前页中存放的记录，类型一般为List

   private long total; //总记录数

   /**
    * 构造方法，只构造空页
    */
   public Page() {
      this(0, 0, DEFAULT_PAGE_SIZE, new ArrayList<T>());
   }

   /**
    * 默认构造方法
    * 
    * @param start 本页数据在数据库中的起始位置
    * @param totalSize 数据库中总记录条数
    * @param pageSize 本页容量
    * @param rows 本页包含的数据
    */
   public Page(long start, long totalSize, int pageSize, List<T> rows) {
      this.pageSize = pageSize;
      this.start = start;
      this.total = totalSize;
      this.rows = rows;
   }

   /**
    * 取总记录数
    */
   public long getTotal() {
      return this.total;
   }
   
   public void setTotal(long total) {
      this.total = total;
   }

   /**
    * 取总页数
    */
   public long getTotalPageCount() {
      if (total % pageSize == 0){
         return total / pageSize;
      }else{
         return total / pageSize + 1;
      }
   }

   /**
    * 取每页数据容量
    */
   public int getPageSize() {
      return pageSize;
   }

   /**
    * 取当前页中的记录
    */
   public List<T> getRows() {
      return rows;
   }
   
   public void setRows(List<T> rows) {
      this.rows = rows;
   }

   /**
    * 取该页的当前页码，页码从1开始
    */
   public long getPageNo() {
      return start / pageSize + 1;
   }

   /**
    * 该页是否有下一页
    */
   public boolean hasNextPage() {
      return this.getPageNo() < this.getTotalPageCount() - 1;
   }

   /**
    * 该页是否有上一页
    */
   public boolean hasPreviousPage() {
      return this.getPageNo() > 1;
   }

   /**
    * 获取任意一页第一条数据在数据集中的位置，每页条数使用默认值
    * 
    * @see #getStartOfPage(int,int)
    */
   protected static int getStartOfPage(int pageNo) {
      return getStartOfPage(pageNo, DEFAULT_PAGE_SIZE);
   }

   /**
    * 获取任意一页第一条数据在数据集中的位置
    * 
    * @param pageNo 从1开始的页号
    * @param pageSize 每页记录条数
    * @return 该页第一条数据
    */
   public static int getStartOfPage(int pageNo, int pageSize) {
      return (pageNo - 1) * pageSize;
   }

}

2.2 ResultMsg#

ResultMsg类主要是为统一返回结果做的顶层设计，主要包括状态码、结果说明内容和返回数据。

package javax.core.common;

import java.io.Serializable;

//底层设计
public class ResultMsg<T> implements Serializable {

   private static final long serialVersionUID = 2635002588308355785L;

   private int status; //状态码，系统的返回码
   private String msg;  //状态码的解释
   private T data;  //放任意结果

   public ResultMsg() {}
   
   public ResultMsg(int status) {
      this.status = status;
   }

   public ResultMsg(int status, String msg) {
      this.status = status;
      this.msg = msg;
   }
   
   public ResultMsg(int status, T data) {
      this.status = status;
      this.data = data;
   }

   public ResultMsg(int status, String msg, T data) {
      this.status = status;
      this.msg = msg;
      this.data = data;
   }

   public int getStatus() {
      return status;
   }

   public void setStatus(int status) {
      this.status = status;
   }

   public String getMsg() {
      return msg;
   }

   public void setMsg(String msg) {
      this.msg = msg;
   }

   public T getData() {
      return data;
   }

   public void setData(T data) {
      this.data = data;
   }

}

2.3 BaseDao#

作为所有BaseDao持久化框架的顶层接口，主要定义增、删、改、查统一的参数列表和返回值。

package javax.core.common.jdbc;

import com.gupaoedu.vip.orm.framework.QueryRule;

import javax.core.common.Page;
import java.util.List;
import java.util.Map;

public interface BaseDao<T,PK> {
    /**
     * 获取列表
     * @param queryRule 查询条件
     * @return
     */
    List<T> select(QueryRule queryRule) throws Exception;

    /**
     * 获取分页结果
     * @param queryRule 查询条件
     * @param pageNo 页码
     * @param pageSize 每页条数
     * @return
     */
    Page<?> select(QueryRule queryRule,int pageNo,int pageSize) throws Exception;

    /**
     * 根据SQL获取列表
     * @param sql SQL语句
     * @param args 参数
     * @return
     */
    List<Map<String,Object>> selectBySql(String sql, Object... args) throws Exception;

    /**
     * 根据SQL获取分页
     * @param sql SQL语句
     * @param pageNo 页码
     * @param pageSize 每页条数
     * @return
     */
    Page<Map<String,Object>> selectBySqlToPage(String sql, Object [] param, int pageNo, int pageSize) throws Exception;

    /**
     * 删除一条记录
     * @param entity entity中的ID不能为空，如果ID为空，其他条件不能为空，都为空则不予执行
     * @return
     */
    boolean delete(T entity) throws Exception;

    /**
     * 批量删除
     * @param list
     * @return 返回受影响的行数
     * @throws Exception
     */
    int deleteAll(List<T> list) throws Exception;

    /**
     * 插入一条记录并返回插入后的ID
     * @param entity 只要entity不等于null，就执行插入操作
     * @return
     */
    PK insertAndReturnId(T entity) throws Exception;

    /**
     * 插入一条记录自增ID
     * @param entity
     * @return
     * @throws Exception
     */
    boolean insert(T entity) throws Exception;

    /**
     * 批量插入
     * @param list
     * @return 返回受影响的行数
     * @throws Exception
     */
    int insertAll(List<T> list) throws Exception;

    /**
     *  修改一条记录
     * @param entity entity中的ID不能为空，如果ID为空，其他条件不能为空，都为空则不予执行
     * @return
     * @throws Exception
     */
    boolean update(T entity) throws Exception;
}

2.4 QueryRule#

如果用QueryRule类来构建查询条件，用户在做条件查询时不需要手写SQL，实现业务代码与SQL解耦。

package com.gupaoedu.vip.orm.framework;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

/**
 * QueryRule，主要功能用于构造查询条件
 */
public final class QueryRule implements Serializable
{
   private static final long serialVersionUID = 1L;
   public static final int ASC_ORDER = 101;
   public static final int DESC_ORDER = 102;
   public static final int LIKE = 1;
   public static final int IN = 2;
   public static final int NOTIN = 3;
   public static final int BETWEEN = 4;
   public static final int EQ = 5;
   public static final int NOTEQ = 6;
   public static final int GT = 7;
   public static final int GE = 8;
   public static final int LT = 9;
   public static final int LE = 10;
   public static final int ISNULL = 11;
   public static final int ISNOTNULL = 12;
   public static final int ISEMPTY = 13;
   public static final int ISNOTEMPTY = 14;
   public static final int AND = 201;
   public static final int OR = 202;
   private List<Rule> ruleList = new ArrayList<Rule>();
   private List<QueryRule> queryRuleList = new ArrayList<QueryRule>();
   private String propertyName;

   private QueryRule() {}

   private QueryRule(String propertyName) {
      this.propertyName = propertyName;
   }

   public static QueryRule getInstance() {
      return new QueryRule();
   }
   
   /**
    * 添加升序规则
    * @param propertyName
    * @return
    */
   public QueryRule addAscOrder(String propertyName) {
      this.ruleList.add(new Rule(ASC_ORDER, propertyName));
      return this;
   }

   /**
    * 添加降序规则
    * @param propertyName
    * @return
    */
   public QueryRule addDescOrder(String propertyName) {
      this.ruleList.add(new Rule(DESC_ORDER, propertyName));
      return this;
   }

   public QueryRule andIsNull(String propertyName) {
      this.ruleList.add(new Rule(ISNULL, propertyName).setAndOr(AND));
      return this;
   }

   public QueryRule andIsNotNull(String propertyName) {
      this.ruleList.add(new Rule(ISNOTNULL, propertyName).setAndOr(AND));
      return this;
   }

   public QueryRule andIsEmpty(String propertyName) {
      this.ruleList.add(new Rule(ISEMPTY, propertyName).setAndOr(AND));
      return this;
   }

   public QueryRule andIsNotEmpty(String propertyName) {
      this.ruleList.add(new Rule(ISNOTEMPTY, propertyName).setAndOr(AND));
      return this;
   }

   public QueryRule andLike(String propertyName, Object value) {
      this.ruleList.add(new Rule(LIKE, propertyName, new Object[] { value }).setAndOr(AND));
      return this;
   }

   public QueryRule andEqual(String propertyName, Object value) {
      this.ruleList.add(new Rule(EQ, propertyName, new Object[] { value }).setAndOr(AND));
      return this;
   }

   public QueryRule andBetween(String propertyName, Object... values) {
      this.ruleList.add(new Rule(BETWEEN, propertyName, values).setAndOr(AND));
      return this;
   }

   public QueryRule andIn(String propertyName, List<Object> values) {
      this.ruleList.add(new Rule(IN, propertyName, new Object[] { values }).setAndOr(AND));
      return this;
   }

   public QueryRule andIn(String propertyName, Object... values) {
      this.ruleList.add(new Rule(IN, propertyName, values).setAndOr(AND));
      return this;
   }
   
   public QueryRule andNotIn(String propertyName, List<Object> values) {
      this.ruleList.add(new Rule(NOTIN, propertyName, new Object[] { values }).setAndOr(AND));
      return this;
   }

   public QueryRule orNotIn(String propertyName, Object... values) {
      this.ruleList.add(new Rule(NOTIN, propertyName, values).setAndOr(OR));
      return this;
   }
   

   public QueryRule andNotEqual(String propertyName, Object value) {
      this.ruleList.add(new Rule(NOTEQ, propertyName, new Object[] { value }).setAndOr(AND));
      return this;
   }

   public QueryRule andGreaterThan(String propertyName, Object value) {
      this.ruleList.add(new Rule(GT, propertyName, new Object[] { value }).setAndOr(AND));
      return this;
   }

   public QueryRule andGreaterEqual(String propertyName, Object value) {
      this.ruleList.add(new Rule(GE, propertyName, new Object[] { value }).setAndOr(AND));
      return this;
   }

   public QueryRule andLessThan(String propertyName, Object value) {
      this.ruleList.add(new Rule(LT, propertyName, new Object[] { value }).setAndOr(AND));
      return this;
   }

   public QueryRule andLessEqual(String propertyName, Object value) {
      this.ruleList.add(new Rule(LE, propertyName, new Object[] { value }).setAndOr(AND));
      return this;
   }
   
   
   public QueryRule orIsNull(String propertyName) {
      this.ruleList.add(new Rule(ISNULL, propertyName).setAndOr(OR));
      return this;
   }

   public QueryRule orIsNotNull(String propertyName) {
      this.ruleList.add(new Rule(ISNOTNULL, propertyName).setAndOr(OR));
      return this;
   }

   public QueryRule orIsEmpty(String propertyName) {
      this.ruleList.add(new Rule(ISEMPTY, propertyName).setAndOr(OR));
      return this;
   }

   public QueryRule orIsNotEmpty(String propertyName) {
      this.ruleList.add(new Rule(ISNOTEMPTY, propertyName).setAndOr(OR));
      return this;
   }

   public QueryRule orLike(String propertyName, Object value) {
      this.ruleList.add(new Rule(LIKE, propertyName, new Object[] { value }).setAndOr(OR));
      return this;
   }

   public QueryRule orEqual(String propertyName, Object value) {
      this.ruleList.add(new Rule(EQ, propertyName, new Object[] { value }).setAndOr(OR));
      return this;
   }

   public QueryRule orBetween(String propertyName, Object... values) {
      this.ruleList.add(new Rule(BETWEEN, propertyName, values).setAndOr(OR));
      return this;
   }

   public QueryRule orIn(String propertyName, List<Object> values) {
      this.ruleList.add(new Rule(IN, propertyName, new Object[] { values }).setAndOr(OR));
      return this;
   }

   public QueryRule orIn(String propertyName, Object... values) {
      this.ruleList.add(new Rule(IN, propertyName, values).setAndOr(OR));
      return this;
   }

   public QueryRule orNotEqual(String propertyName, Object value) {
      this.ruleList.add(new Rule(NOTEQ, propertyName, new Object[] { value }).setAndOr(OR));
      return this;
   }

   public QueryRule orGreaterThan(String propertyName, Object value) {
      this.ruleList.add(new Rule(GT, propertyName, new Object[] { value }).setAndOr(OR));
      return this;
   }

   public QueryRule orGreaterEqual(String propertyName, Object value) {
      this.ruleList.add(new Rule(GE, propertyName, new Object[] { value }).setAndOr(OR));
      return this;
   }

   public QueryRule orLessThan(String propertyName, Object value) {
      this.ruleList.add(new Rule(LT, propertyName, new Object[] { value }).setAndOr(OR));
      return this;
   }

   public QueryRule orLessEqual(String propertyName, Object value) {
      this.ruleList.add(new Rule(LE, propertyName, new Object[] { value }).setAndOr(OR));
      return this;
   }
   

   public List<Rule> getRuleList() {
      return this.ruleList;
   }

   public List<QueryRule> getQueryRuleList() {
      return this.queryRuleList;
   }

   public String getPropertyName() {
      return this.propertyName;
   }

   protected class Rule implements Serializable {
      private static final long serialVersionUID = 1L;
      private int type;  //规则的类型
      private String property_name;
      private Object[] values;
      private int andOr = AND;

      public Rule(int paramInt, String paramString) {
         this.property_name = paramString;
         this.type = paramInt;
      }

      public Rule(int paramInt, String paramString,
            Object[] paramArrayOfObject) {
         this.property_name = paramString;
         this.values = paramArrayOfObject;
         this.type = paramInt;
      }
      
      public Rule setAndOr(int andOr){
         this.andOr = andOr;
         return this;
      }
      
      public int getAndOr(){
         return this.andOr;
      }

      public Object[] getValues() {
         return this.values;
      }

      public int getType() {
         return this.type;
      }

      public String getPropertyName() {
         return this.property_name;
      }
   }
}

2.5 Order#

Order类主要用于封装排序规则，代码如下：

package com.gupaoedu.vip.orm.framework;

/**
 * SQL排序组件
 */
public class Order {
   private boolean ascending; //升序还是降序
   private String propertyName; //哪个字段升序，哪个字段降序
   
   public String toString() {
      return propertyName + ' ' + (ascending ? "asc" : "desc");
   }

   /**
    * Constructor for Order.
    */
   protected Order(String propertyName, boolean ascending) {
      this.propertyName = propertyName;
      this.ascending = ascending;
   }

   /**
    * Ascending order
    *
    * @param propertyName
    * @return Order
    */
   public static Order asc(String propertyName) {
      return new Order(propertyName, true);
   }

   /**
    * Descending order
    *
    * @param propertyName
    * @return Order
    */
   public static Order desc(String propertyName) {
      return new Order(propertyName, false);
   }
}

因篇幅原因，具体的操作类下一篇继续。

出　　处：https://www.cnblogs.com/gupaoedu-tom/p/15697485.html