Displaying all submitted records for an approval process along with their status in VF Page

Few days back, I got requirement from one of my friends to list all approval process in Visualforce Page in picklist and when user select any approval process, the system should display all the records which are submitted for approval along with their status.
In order to achieve this, I have created a VF page and used REST API to get list of all approval process present in org. After getting the list of approval process in JSON, I parsed the response and displayed the approval process names in picklist. When user select particular approval process, system will query all processinstances records and then with the help of TargetObjectid, it will fetched the Ojbect name. Then system will match the object name related to approval process with object related to targetobjectid.
If it got matched, then processInstance record will be stored in list and will be displayed to user.

VF Page Snapshot:

Notes:

• First create remote site setting with Remote Site URL as https://xxx.salesforce.com where xxx domain name like ap1,na1 etc.
• I tried to filter the number of processInstance records by putting where clause but it didn't work for me. So I queried all processInstance records.
• We can specify where clause on createddate or lastmodifieddate by giving an option to user to select date range. We can display two more fields as startdate and enddate on VF page and system will display only processinstance records created or modified between these 2 dates.

Looking forward to your comments and suggestions.

Below is VF Page Code:

<apex:page controller="DisplayApprovedRecordsController" action="{!FetchAllApprovalProcess}">
<apex:form >
    <apex:pageblock title="Approval processess List">      
        <apex:pageblocksection columns="3">
            <apex:pageblockSectionItem >
                <apex:outputLabel value="Select" for="apr"></apex:outputLabel>
                <apex:selectList value="{!selectedApprovalProcess}" size="1" id="apr">
                    <apex:selectOptions value="{!ApprovalWrapperList}"></apex:selectOptions>
                    <apex:actionsupport event="onchange" action="{!FindRecords}"/>
                </apex:selectList>
            </apex:pageblockSectionItem>          
        </apex:pageblocksection>      
        <apex:pageblockSection title="Approved Records" columns="1" >
            <apex:pageblockTable value="{!recordList}" var="rec" rendered="{!recordList.size>0}">
                <apex:column headerValue="Name">
                    <apex:outputlink value="/{!rec.TargetObjectId}">{!rec.TargetObject.name}</apex:outputlink>
                </apex:column>              
                <apex:column headerValue="Status">
                    <apex:outputText value="{!rec.status}"></apex:outputText>
                </apex:column>
            </apex:pageblockTable>          
            <apex:outputpanel rendered="{!recordList.size==0}">
                <apex:outputText value="No records to display"></apex:outputText>
            </apex:outputpanel>      
        </apex:pageblockSection>
    </apex:pageblock>
</apex:form>
</apex:page>

Apex Class Code:

public class DisplayApprovedRecordsController {
    public List<ApprovalWrapper> ApprovalProcessList{get;set;}//list to store all approval process
    public String selectedApprovalProcess{get;set;}
    Public list<ProcessInstance> recordList{get;set;} //list to store processInstance records to display on UI

    public List<selectoption> getApprovalWrapperList(){
        List<selectoption> temp=new List<selectoption>();
        temp.add(new selectoption('','--Select--'));
        for(String ap:approvalMap.keyset()){
            temp.add(new selectoption(ap,ap));
        }
        return temp;
    }
    public DisplayApprovedRecordsController (){
        ApprovalProcessList=new List<ApprovalWrapper>();
        recordList=new list<ProcessInstance> ();
    }
    public map<String,ApprovalWrapper> approvalMap=new map<String,ApprovalWrapper>();
    public void FetchAllApprovalProcess(){      
        HttpRequest req = new HttpRequest();
        req.setHeader('Authorization', 'Bearer ' + UserInfo.getSessionID());
        req.setHeader('Content-Type', 'application/json');
        String domainUrl=URL.getSalesforceBaseUrl().toExternalForm();
        system.debug('********domainUrl:'+domainUrl);
        String endpointUrl=domainUrl+'/services/data/v30.0/process/approvals/';
        req.setEndpoint(endpointUrl);
        req.setMethod('GET');      
        Http h = new Http();
        HttpResponse res = h.send(req);
        system.debug(res.getBody());
        String ss=res.getBody();
        string newjsondata = ss.replace('"object"','"objectName"');
       
        // Parse entire JSON response.
        JSONParser parser = JSON.createParser(newjsondata );
        while (parser.nextToken() != null) {
            // Start at the array of invoices.
            if (parser.getCurrentToken() == JSONToken.START_ARRAY) {
                while (parser.nextToken() != null) {
                    // Advance to the start object marker to
                    //  find next approval process object.
                    if (parser.getCurrentToken() == JSONToken.START_OBJECT) {
                        // Read entire  approval process object
                        ApprovalWrapper apr= (ApprovalWrapper)parser.readValueAs(ApprovalWrapper.class);
                        system.debug('Approval name: ' + apr.name);
                        system.debug('Id: ' + apr.id);
                        ApprovalProcessList.add(apr);
                        // Skip the child start array and start object markers.
                        parser.skipChildren();
                    }
                }
            }
        }
        system.debug('********ApprovalProcessList:'+ApprovalProcessList);
        for(ApprovalWrapper aw:ApprovalProcessList){
            approvalMap.put(aw.name,aw);
        }
}
public Pagereference FindRecords(){
recordList=new list<ProcessInstance> ();
        if(selectedApprovalProcess!=null && selectedApprovalProcess!=''){
            recordList=new list<ProcessInstance> ();
            String queryString='Select Id, TargetObjectId,TargetObject.name, Status From ProcessInstance Limit 10000';
            System.debug('*********queryString:'+queryString);
            List<ProcessInstance> temp=Database.query(queryString);
            ApprovalWrapper aw=new ApprovalWrapper();
            aw=approvalMap.get(selectedApprovalProcess);
            String ObjName=aw.objectName;
            recordList=new List<Processinstance>();
            For(ProcessInstance sb:temp){
                String ObjectName=String.valueof(sb.TargetObjectId.getSObjectType());
                system.debug('****ObjectName:'+ObjectName);
                if(Objectname.equalsignorecase(ObjName)){
                    recordList.add(sb);
                }
            }
            System.debug('*********recordList:'+recordList);
       }
        return null;
    }    
    public class ApprovalWrapper{
        public String description{get;set;}
        public String id{get;set;}
        public String name{get;set;}
        public String objectName{get;set;}
        public Integer sortOrder{get;set;}
    }
}