How to convert ResultSet to Java objects

sometimes we don't want to use any framework, but we need The JDBC implementation is similar to Ibatis's ORM mapping function, transforms a resultset into our javabeans, we can imitate the ibatis way oneself writes a resultsetmapper realization class, Using the principle of reflection to convert resultset into a JavaBeans, the following is an open-source implementation of the Internet, the main use is AnnotationsAnd ReflectionMechanism, let's look at the use effect:

Package Com.heaven.mapper;import Java.sql.connection;import Java.sql.drivermanager;import Java.sql.preparedstatement;import Java.sql.resultset;import Java.sql.sqlexception;import Java.util.List;public Class Samplemain {public static void main (String ... args) {try {resultsetmapper<samplepojo> resultsetmapper = new Re Sultsetmapper<samplepojo> (); ResultSet ResultSet = null;//Simple JDBC code to run SQL query and populate Resultset-startclass.forname ("Sun.jdbc.odbc . Jdbcodbcdriver "); String database = "Jdbc:odbc:AkDb"; Connection Connection = drivermanager.getconnection (Database, "", ""); PreparedStatement statement = connection.preparestatement ("SELECT * from Userssample"); ResultSet = Statement.executequery ();/******************************/list<samplepojo> pojoList = Resultsetmapper.maprersultsettoobject (ResultSet, Samplepojo.class);/******************************/if (pojoList!) = null) {for (Samplepojo pojo:pojolist) {System.out.println (Pojo);}} Else{system.out.println ("ResULtset is empty. Please check if the database table is empty "); Connection.close ();} catch (ClassNotFoundException e) {e.printstacktrace ();} catch (SQLException e) {e.printstacktrace ()}}}

As shown, converting resultset to our Javapojo object requires only one method of calling Resultsetmapper, which is very convenient to use.Below isresultsetmapper Source code:

Package Com.heaven.mapper;import Java.lang.reflect.field;import java.lang.reflect.InvocationTargetException; Import Java.sql.resultset;import Java.sql.resultsetmetadata;import Java.sql.sqlexception;import Java.util.arraylist;import Java.util.list;import Javax.persistence.column;import Javax.persistence.Entity;import Org.apache.commons.beanutils.beanutils;public class Resultsetmapper<t> {@SuppressWarnings ("unchecked")  Public list<t> Maprersultsettoobject (ResultSet rs, Class outputclass) {list<t> outputlist = null;try {//Make Sure ResultSet is not nullif (rs! = null) {//Check if Outputclass has ' Entity ' annotationif (outputclass.isannotationpre Sent (Entity.class)) {//Get the resultset metadataresultsetmetadata RSMD = Rs.getmetadata ();//Get all the attributes of O utputclassfield[] fields = Outputclass.getdeclaredfields (), while (Rs.next ()) {T bean = (T) outputclass.newinstance (); for (int _iterator = 0; _iterator < Rsmd.getcolumncount (); _iterator++) {//Getting the SQL column Namestring columnName = rsmd.getcolumnname (_iterator + 1);//reading the value of the SQL columnobject Columnvalu E = Rs.getobject (_iterator + 1);//iterating over Outputclass attributes to check if//any attribute have ' Column ' Annotati On with//matching ' name ' valuefor (Field field:fields) {if (Field.isannotationpresent (Column.class)) {Column Column = f Ield.getannotation (Column.class); if (Column.name (). Equalsignorecase (columnName) && columnvalue! = null) { Beanutils.setproperty (Bean, Field.getname (), columnvalue); break;}}}} if (outputlist = = null) {outputlist = new arraylist<t> ();} Outputlist.add (bean);}} else {//Throw some error}} else {return null;}} catch (Illegalaccessexception e) {e.printstacktrace ();} catch (SQLException e) {e.printstacktrace ();} catch ( Instantiationexception e) {e.printstacktrace ();} catch (InvocationTargetException e) {e.printstacktrace ();} return outputlist;}}

Pojo objects that use annotations:

<pre name= "code" class= "java" >package com.heaven.mapper;import Javax.persistence.column;import javax.persistence.Entity; @Entitypublic class Samplepojo {@Column (name= "user_id") private int Id; @Column (name= "User_ Name ") private string name; @Column (name=" address ") private string address; @Column (name=" Gender ") Private Boolean Gender ;p ublic int getId () {return ID;} public void setId (int id) {this.id = ID;} Public String GetName () {return name;} public void SetName (String name) {this.name = name;} Public String getaddress () {return address;} public void setaddress (String address) {this.address = address;} public Boolean Isgender () {return gender;} public void Setgender (Boolean gender) {This.gender = gender;} @Overridepublic String toString () {return ID: "+ id +" \ n "+" name: "+ name +" \ n "+" Address: "+ address +" \ n "+" Gende R: "+ (gender?") Male ":" Female ") +" \ n ";}}

How to convert ResultSet to Java objects