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网上关于mybatis的拦截器文章有不少，但都大同小异，如果想做一个通用mapper和关系映射的查询都不太能够解决问题，所以自己就花了些时间写了一个mybatis的扩展（目前只实现了mysql数据库），具体项目可以在上下载。

先简单介绍一下扩展使用，后面在陆续展开说明实现

1. 实体类定义
   假定数据三张表：公司、部门、员工，定义如下：
    

   public abstract class BaseEntity extends BaseExtEntity {    public enum CommonStatus implements BaseExtEnum {        Enable(1, "正常"),        Disable(0, "关闭");        private int value;        private String name;        private CommonStatus(int value, String name){            this.value = value;            this.name = name;        }        @Override        public Object getValue() {            return value;        }        @Override        public String getName() {            return name;        }    }}

   @Table("Company")public class CompanyEntity extends BaseEntity {    @Column(primaryKey = true)    private int id;    @Column    private String comName;    @Column    private Date registerDate;    @Column("ComAddress")    private String address;    @Column    private CommonStatus status;    @OneMany(type = DepartmentEntity.class, foreignKey = "comId", propertyKey = "id")    private List
        
          departments;    private int countValue;    public int getId() {        return id;    }    public Date getRegisterDate() {        return registerDate;    }    public String getAddress() {        return address;    }    public String getComName() {        return comName;    }    public CommonStatus getStatus() {        return status;    }    public int getCountValue() {        return countValue;    }    public List
         
           getDepartments() {        return departments;    }    public void setId(int id) {        this.id = id;    }    public void setAddress(String address) {        this.address = address;    }    public void setComName(String comName) {        this.comName = comName;    }    public void setRegisterDate(Date registerDate) {        this.registerDate = registerDate;    }    public void setStatus(CommonStatus status) {        this.status = status;    }    public void setCountValue(int countValue) {        this.countValue = countValue;    }    public void setDepartments(List
          
            departments) {        this.departments = departments;    }}
          
         
        

   @Table("Department")public class DepartmentEntity extends BaseEntity {    @Column(primaryKey = true)    private int id;    @Column    private int comId;    @Column    private String departmentName;    @OneOne(type = CompanyEntity.class, foreignKey = "id", propertyKey = "comId")    private CompanyEntity company;    @OneMany(type = EmployeeEntity.class, foreignKey = "departmentId", propertyKey = "id")    private List
        
          employees;}
        

   @Table("Employee")public class EmployeeEntity extends BaseEntity {    @Column(primaryKey = true, generatedKey = false)    private String id;    @Column    private String name;    @Column    private Gender gender;    @Column    private int level;    @Column    private String title;    @Column    private int departmentId;    @OneOne(type = DepartmentEntity.class, foreignKey = "id", propertyKey = "departmentId")    private DepartmentEntity department;    public enum Gender implements BaseExtEnum {        Male(1, "男"),        Female(2, "女");        private int value;        private String name;        private Gender(int value, String name){            this.value = value;            this.name = name;        }        @Override        public Object getValue() {            return value;        }        @Override        public String getName() {            return name;        }    }}

    

2. mapper
    

   public interface BaseMapper
        
          extends BaseExtMapper
         
           {}
         
        

   public interface CompanyMapper extends BaseMapper
        
          {}
        

   public interface DepartmentMapper extends BaseMapper
        
          {}
        

   public interface EmployeeMapper extends BaseMapper
        
          {}
        

    
3. 基础增删改查操作
    

   @Autowiredprivate CompanyMapper companyMapper;companyMapper.addOne(entity);companyMapper.addMany(entities);companyMapper.removeById(id);companyMapper.removeByIds(ids);companyMapper.updateById(entity);companyMapper.getById(id);companyMapper.getByIds(ids);

    
4. 特定条件及表连接操作
    

   //更新MySqlStatement mySqlStatement = MySqlStatement.createUpdateStatement(YourEntity.class);mySqlStatement        .set("propertyName", "propertyValue")        .where("propertyName", ConditionType.EQUAL, "propertyValue");int result = mapper.update(mySqlStatement);//删除MySqlStatement mySqlStatement = MySqlStatement.createDeleteStatement(YourEntity.class);mySqlStatement        .where("propertyName", ConditionType.EQUAL, "propertyValue");int result = mapper.remove(mySqlStatement);//单表查询MySqlStatement mySqlStatement = MySqlStatement.createSelectStatement(YourEntity.class);mySqlStatement.select("id", "name");mySqlStatement.select("id", "name");YourEntity entity = mapper.getOne(mySqlStatement);mySqlStatement.orderBy("id", OrderType.DESCENDING).limit(10);List
        
          entities = mapper.getMany(mySqlStatement);MySqlStatement mySqlStatement = MySqlStatement.createSelectStatement(YourEntity.class);mySqlStatement.select("max(#{id})");YourEntity entity = mapper.getOne(mySqlStatement);int maxId = entity.getId();MySqlStatement mySqlStatement = MySqlStatement.createSelectStatement(YourEntity.class);mySqlStatement.selectAs("count(#{id})", "propertyName");YourEntity entity = mapper.getOne(mySqlStatement);int countNum = entity.getPropertyName();//表连接查询MySqlStatement mySqlStatement = MySqlStatement.createSelectStatement(YourEntity1.class);MySqlStatement mySqlStatement1 = mySqlStatement.createSubQuery("relationshipProperty");MySqlStatement mySqlStatement2 = mySqlStatement.createSubQuery(YourEntity2.class);mySqlStatement.join(mySqlStatement2, JoinType.LEFT_JOIN, "fromPropertyName", "toPropertyName", false, "resultPropertyName");mySqlStatement1.select("id", "name");mySqlStatement2.select("id", "name");//子查询MySqlStatement mySqlStatement = MySqlStatement.createSelectStatement(YourEntity1.class);MySqlStatement mySqlStatement2 = mySqlStatement.createSubQuery(YourEntity2.class);mySqlStatement.join(mySqlStatement2, JoinType.LEFT_JOIN, "fromPropertyName", "toPropertyName", true, "resultPropertyName");//分页查询Pager pager = new Pager();pager.setPageSize(10);pager.setCurrentPage(1);    List
         
           entities = getPage(mySqlStatement, pager);pager.getRowCount();pager.getCurrentPage();//获取查询sql及参数FormatSqlWrapper formatSqlWrapper = mySqlStatement.getFormatSqlWrapper();formatSqlWrapper.getSql();formatSqlWrapper.getParameters();
         
        

暂时先介绍这么多，下一篇开始阐述具体实现，源代码。

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