数据表与简单Java类映射（内容不全）

亦凉 2023-01-06 01:17 94阅读 0赞

## 概念 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIxNDgwNjA3_size_16_color_FFFFFF_t_70]  
对于数据表与简单java类之间的映射最好的解决步骤，先抛开所有的关联字段不看，写出本类的基本组成，而后通过引用配置关联字段的关系。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIxNDgwNjA3_size_16_color_FFFFFF_t_70 1]

## 例子 ##

第一步 根据表的结构关系进行对象的配置

第二步 根据要求通过结构获取数据  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIxNDgwNjA3_size_16_color_FFFFFF_t_70 2]

package com.msc.example;
    
    import javax.swing.*;
    
    class Privilege{ 
       private long pid ;
       private String pname ;
       private Role roles[] ;
       public Privilege() { };
       public Privilege(long pid,String pname){ 
           this.pid = pid ;
           this.pname = pname ;
       }
       public void setRoles(Role[] roles) { 
            this.roles = roles;
        }
       public void setPid(long pid) { 
            this.pid = pid;
        }
       public void setPname(String pname) { 
            this.pname = pname;
        }
       public long getPid() { 
            return pid;
        }
       public Role[] getRoles() { 
            return roles;
        }
       public String getPname() { 
            return pname;
        }
       public String getInfo(){ 
           return "【权限信息】 权限ID = " + this.pid + ",权限名称 = " + this.pname;
        }
    }
    class Role{ 
       private long rid ;
       private String rname ;
       private Member members[] ;
       private Privilege privileges[] ;
       public Role() { } ;
       public Role(long rid,String rname){ 
           this.rid = rid ;
           this.rname = rname ;
       }
       public long getRid() { 
            return rid;
        }
       public void setRid(long rid) { 
            this.rid = rid;
        }
       public String getRname() { 
            return rname;
        }
       public void setRname(String rname) { 
            this.rname = rname;
        }
       public Member[] getMembers() { 
            return members;
        }
       public void setMembers(Member[] members) { 
            this.members = members;
        }
       public Privilege[] getPrivileges() { 
            return privileges;
        }
       public void setPrivileges(Privilege[] privileges) { 
            this.privileges = privileges;
        }
        public String getInfo(){ 
            return "【角色信息】 角色ID = " + this.rid + ",角色名字 = " + this.rname;
        }
    }
    class Member{ 
        private long mid ;
        private String mname ;
        private Role roles[] ;
        public Member() { } ;
        public  Member(long mid,String mname){ 
            this.mid = mid ;
            this. mname = mname ;
        }
        public void setRoles(Role[] roles) { 
            this.roles = roles;
        }
        public Role[] getRoles() { 
            return roles;
        }
        public long getMid() { 
            return mid;
        }
        public void setMid(long mid) { 
            this.mid = mid;
        }
        public String getMname() { 
            return mname;
        }
        public void setMname(String mname) { 
            this.mname = mname;
        }
        public String getInfo(){ 
            return "【用户信息】 用户ID = " + this.mid + "，用户姓名 = " + this.mname;
        }
    }
    
    public class MapDemo { 
        public static void main(String[] args) { 
     
            memA.setRoles(new Role[]{ roleA,roleC});
            memB.setRoles(new Role[]{ roleB});
            memC.setRoles(new Role[]{ roleD});
            memD.setRoles(new Role[]{ roleB});
    
            roleA.setMembers(new Member[]{ memA});
            roleB.setMembers(new Member[]{ memB,memC});
            roleC.setMembers(new Member[]{ memA});
            roleD.setMembers(new Member[]{ memD});
    
            roleA.setPrivileges(new Privilege[]{ priA,priC});
            roleB.setPrivileges(new Privilege[]{ priA,priB,priC});
            roleC.setPrivileges(new Privilege[]{ priC});
            roleD.setPrivileges(new Privilege[]{ priA});
    
            priA.setRoles(new Role[]{ roleA,roleB,roleD});
            priB.setRoles(new Role[]{ roleB});
            priC.setRoles(new Role[]{ roleC});
            System.out.println("--------用户找角色+权限: "+memA.getMname()+"-------------");
            for(Role role : memA.getRoles()){ 
                System.out.println(memA.getInfo()+role.getInfo());
                for(Privilege pri : role.getPrivileges()){ 
                    System.out.println(" "+pri.getInfo());
                }
            }
    
        /* for(int i = 0 ; i < memA.getRoles().length;i++){ System.out.println(memA.getInfo()+memA.getRoles()[i].getInfo()); for(int j = 0 ; j < memA.getRoles()[i].getPrivileges().length;j++){ System.out.println(" "+memA.getRoles()[i].getPrivileges()[j].getInfo()); } }*/
            System.out.println("-------------角色找用户权限: "+roleB.getRname()+"-------------");
            System.out.println(roleB.getInfo());
            for(Member mem : roleB.getMembers()){ 
                System.out.println(" " + mem.getInfo());
            }
            for (Privilege pri : roleB.getPrivileges()){ 
                System.out.println(" " + pri.getInfo());
            }
            System.out.println("------------根据权限找用户："+priB.getPname()+"-------------");
            for(Role role : priB.getRoles()){ 
                for(Member mem : role.getMembers()){ 
                    System.out.println(" " + mem.getInfo());
                }
            }
        }
    }

**输出**

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIxNDgwNjA3_size_16_color_FFFFFF_t_70]: /images/20221119/1507616a30034e34b8435e5dd062c6eb.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIxNDgwNjA3_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20210113153826130.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIxNDgwNjA3,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIxNDgwNjA3_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20210113154103445.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIxNDgwNjA3,size_16,color_FFFFFF,t_70