A proxy class that connects MyBatis internal sqlsession with the business interface Mapperproxy

Objective

When the business interface in the system needs to call MyBatis's SQL, the parameters defined by the business interface do not conform to MyBatis's own internal specifications, then the parameters of the business interface need to be converted into MyBatis internal parameter gauges, and the Mapperproxy agent completes this duty. Here's a look at the analysis.

Public object invoke (Object proxy, method method, object[] args)   throws throwable {    if  (Object.class.equals (Method.getdeclaringclass ()))  {      try {        return  method.invoke (This, args);      } catch  (Throwable t)  {        throw exceptionutil.unwrapthrowable (t);       }    }    final MapperMethod  Mappermethod = cachedmappermethod (method);     return mappermethod.execute ( Sqlsession, args);} Private mappermethod cachedmappermethod (Method method)  {     Mappermethod mappermethod = methodcache.get (method);    if  ( Mappermethod ==&nbSp;null)  {      mappermethod = new mappermethod ( Mapperinterface, method, sqlsession.getconfiguration ());       Methodcache.put (Method, mappermethod);    }    return  Mappermethod;}

The above invoke is the proxy class callback method, and the Cachedmappermethod method does a cache. Here the constructor of the Mappermethod class and the Execute method of the Mappermethod class are the main logic, first look at the Mappermethod constructor.

1 Mappermethod Constructors

There are 2 classes instantiated, and the 2 classes are analyzed according to the query in the diagram.

Public sqlcommand (Configuration configuration, class<?> mapperinterface, method  method)  throws BindingException {      //  cn.vansky.schedule.time.menu.dao.menumapper.findmenubyuserid      string  Statementname = mapperinterface.getname ()  +  "."  + method.getname ();      mappedstatement ms = null;       if  (Configuration.hasstatement (statementname))  {         ms = configuration.getmappedstatement (StatementName);       } else if  (!mapperinterface.equals (Method.getdeclaringclass). GetName ())  { // issue  #35         String  Parentstatementname = method.getdeclaringclass (). GetName ()  +  "." &nBsp;+ method.getname ();        if  ( Configuration.hasstatement (parentstatementname))  {           ms = configuration.getmappedstatement (Parentstatementname);         }      }      if  (ms = = null)  {        throw new bindingexception (" invalid bound statement  (Not found):  " + statementname);       }      //  cn.vansky.schedule.time.menu.dao.menumapper.findmenubyuserid      name =  ms.getid ();       // select      type  = ms.getsqlcommandtype ();      if  (Type == SQlcommandtype.unknown)  {        throw new  Bindingexception ("unknown execution method for: "  + name);       }}public methodsignature (Configuration configuration, method method)  throws BindingException {      //  return value type class       // interface java.util.List       This.returntype = method.getreturntype ();      //  has no return value  true : None, False:       // false       This.returnsvoid = void.class.equals (This.returntype);      //  Whether the return type is a collection collection or an array       // true       this.returnsmany =  (Configuration.getobjectfactory (). IsCOllection (this.returntype)  | |  this.returntype.isarray ());      //  return type is map, get annotations mapkey       //  above method call with a value of null      this.mapkey =  Getmapkey (method);      //  whether the return type is map      //  false      this.returnsMap =  (This.mapkey != null); The       //  parameter has @param annotations       // true       this.hasnamedparameters = hasnamedparams (method);       // null      this.rowBoundsIndex =  Getuniqueparamindex (Method, rowbounds.class);      // null       this.resulthandlerindex = getuniqueparamindex (method,  Resulthandler.class);      //  get parameter list       // 0 ->  userId       this.params =  Collections.unmodifiablesortedmap (Getparams (Method, this.hasnamedparameters));}

The SqlCommand class gets the unique identity of the processing and the SQL statement type, and the Methodsignature class handles the entry type and the parameter type of the business interface method.

2 mappermethed Execution entry-->execute method

Public object execute (Sqlsession sqlsession, object[] args)  {     Object result;    if  (Sqlcommandtype.insert == command.gettype () )  {      //  New       object param  = method.convertargstosqlcommandparam (args);      result =  Rowcountresult (Sqlsession.insert (Command.getname (),  param));     } else if   (Sqlcommandtype.update == command.gettype ())  {      //   Modify       object param = method.convertargstosqlcommandparam ( args);       result = rowcountresult (Sqlsession.update (Command.getName ( );    } else if  (sqlcommandtype.delete == ,  param)) Command.gettype ())  {      //  Delete       Object param =  Method.convertargstosqlcommandparam (args);      result =  Rowcountresult (Sqlsession.delete (Command.getname (),  param));     } else if   (Sqlcommandtype.select == command.gettype ())  {      //   Inquiries       if  (method.returnsvoid ()  &&  Method.hasresulthandler ())  {        //  no return value void         executewithresulthandler (Sqlsession, args);         result = null;      } else if  ( Method.returnsmany ())  {        //  set collection or array          result =&Nbsp;executeformany (Sqlsession, args);      } else if  ( Method.returnsmap ())  {        // Map         result = executeformap (Sqlsession, args);       } else {        //  Unique Results          object param = method.convertargstosqlcommandparam (args);         result = sqlsession.selectone (Command.getName (),  param);       }    } else {       throw new bindingexception ("unknown execution method for: "  +  Command.getname ());    }    if  (result == null  && method.getreTurntype (). Isprimitive ()  && !method.returnsvoid ())  {       throw new bindingexception ("mapper method " " + command.getname ()             +  " attempted to return  null from a method with a primitive return type  (" +  Method.getreturntype ()  +  ").");     }    return result;}

Add (INSERT), change (UPDATE), delete (delete), these 3 kinds of operations can be summed up as one, first, the actual entry of the business interface into the MyBatis internal parameters, and then call the Sqlsession processing method, the results are processed, and return the results.

Check (SELECT) has 4 cases.

One: no return value

Two: Return is a collection of collection or arrays

Three: Return is map

Four: Returns a result

Details of 4 cases are no longer analyzed.

Summarize

First of all, we need to turn the actual import parameters of the business interface into the MyBatis internal parameter, then call the sqlsession corresponding processing method, and finally processing the return result, return to the business interface.

A proxy class that connects MyBatis internal sqlsession with the business interface Mapperproxy