Java Annotations Project is simulated hibenernate generate SQL statement

Compiled some of the recent Java annotations , using Java annotations to emulate the Hibenernate ORM model to build the mapping of objects to SQL statements

Creation of Table annotations

Package Com.imooc.test;import Java.lang.annotation.elementtype;import Java.lang.annotation.retention;import Java.lang.annotation.retentionpolicy;import Java.lang.annotation.target;import javax.lang.model.element.Element ;//used as the annotation for a class, the life cycle is a runtime value @target ({elementtype.type}) @Retention (retentionpolicy.runtime) public @interface Table { String value ();}

Creation of field annotations

Package Com.imooc.test;import Java.lang.annotation.elementtype;import Java.lang.annotation.retention;import Java.lang.annotation.retentionpolicy;import * */@Target ({) When the scope is run for a field java.lang.annotation.target;/* Elementtype.field}) @Retention (retentionpolicy.runtime) public @interface Column {String value ();}

User table (Class)

package com.imooc.test; @Table ("user") public class filter {  @Column ("id")  private  int id;   @Column ("user_name")  private String userName;   @Column ( "user_name")  private String nickName;   @Column ("Age")  private int age;    @Column ("City")  private String city;   @Column ("email")  private  string email;   @Column ("mobile")  private string mobile; public int  getid ()  {  return id; } public void setid (int id)  {   this.id = id; } public string getusername ()  {  return  username; } public void setusername (String username)  {   This.username = username; } public string getnickname ()  {  return  nickname; }&nbSp;public void setnickname (String nickname)  {  this.nickName =  Nickname; } public int getage ()  {  return age; } public  void setage (int age)  {  this.age = age; } public  String getcity ()  {  return city; } public void setcity (String  city)  {  this.city = city; } public string getemail ()   {  return email; } public void setemail (String email)  {   this.email = email; } public string getmobile ()  {  return  mobile; } public void setmobile (String mobile)  {  this.mobile  = mobile; }}

Creating a Test class

Package Com.imooc.test, @Table ("Coder") public class Coder {@Column ("id") private int id; @Column ("name") Private String UserName; @Column ("Age") private int age;public int getId () {return ID;} public void setId (int id) {this.id = ID;} Public String GetUserName () {return userName;} public void Setusername (String userName) {this.username = UserName;} public int getage () {return age;} public void Setage (int.) {this.age = age;}}

The generation process of SQL statements

package com.imooc.test;import java.lang.reflect.field;import  Java.lang.reflect.invocationtargetexception;import java.lang.reflect.method;public class test  { public static void main (String[] args)  {  //  How the code maps to the database   filter f1 = new filter ();   f1.setid (  FILTER F2);  = new filter ();   f2.setusername ("Lucy");   filter f3 = new  filter ();   f3.setemail ("[email protected],[email protected],[email protected]") ;   coder c1 = new coder ();   c1.setusername ("Ruanjianlin");   String sql1 = query (F1);   string sql2 = query (F2);   String  sql3 = query (F3);   string sql4 = query (C1);   System.out.println (SQL1);   system.out.println (SQL2);    system.out.println (SQL3);   system.out.println (SQL4); } private static  String query (object f)  {  // todo auto-generated method stub   stringbuilder sb = new stringbuilder ();   // 1. Gets the class's details by class by class type   class c = f.getclass ();  // java  Package.isannotationpresent () method usage Example Tutorial. The,  //  method returns True if a comment of the specified type exists on this element or returns FALSE  // 2. Gets the name of the table   boolean  exists = c.isannotationpresent (Table.class);  if  (!exists)  {    return null;  }  Table t =  (Table)  c.getannotation ( Table.class);   string tablename = t.value ();   sb.append ("Select* from   "). Append (TableName). Append ("  where 1=1  ");   // 3 traverse all fields   field[]  farray =&Nbsp;c.getdeclaredfields ();  for  (Field field : farray)  {     4 get sql   // 4.1 field name corresponding to each field    boolean fExists =  Field.isannotationpresent (Column.class);//  exists    //  determines if there is a field    if   (!fexists)  {    continue;   }   Column  Column = field.getannotation (Column.class);   string columnname =  Column.value ();   object fieldvalue = null;   string  Filedname = field.getname ();    // 4.2 Get the field value (Get the field's Get method first)    string  getMethodName =  "Get"      + filedname.substring (0, 1). toUpperCase ()      + filedname.substring (1);   try {     Method getMethod = c.getmethod (Getmethodname);//  Gets the value     //  the reflection channel to get the field value      fieldvalue = getmethod.invoke (f);   } catch  (SecurityException e )  {    // TODO Auto-generated catch block     E.printstacktrace ();   } catch  (nosuchmethodexception e)  {     // todo auto-generated catch block    e.printstacktrace ();    } catch  (illegalargumentexception e)  {    //  Todo auto-generated catch block    e.printstacktrace ();    }  catch  (illegalaccessexception e)  {    // TODO  Auto-generated catch block    e.printstacktrace ();    } catch   (Invocationtargetexception&nbsP;e)  {    // TODO Auto-generated catch block     e.printstacktrace ();   }   if  (fieldvalue == null      | |   (fieldvalue instanceof integer &&  (Integer)  fieldvalue == 0))  {    continue;   }   //4.3 assembled sql    Sb.append ("and "). Append (ColumnName);   if  (fieldvalue instanceof string)  {    if  ((String)  fieldvalue). Contains (","))  {      String[] values =  (String)  fieldvalue. Split (",");      sb.append (" in (");     for  (string v : values)  {       sb.append ("'"). Append (v). Append ("',");      }       sb.deletecharat (Sb.length ()  - 1);      sb.append (")");     } else {     sb.append ("= "). Append ( Fieldvalue). Append ("'");    }   } else {     Sb.append ("="). Append (Fieldvalue.tostring ());   }  }  return  Sb.tostring ();  }}

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Java Annotations Project is simulated hibenernate generate SQL statement