[SalesForce] reRender attribute within component

You can use an actionRegion to define a scope for a commandButton or commandLink. This is sufficient to allow inputFile to happily co-exist with reRender attributes. Note that the actionRegion must contain all the information necessary to update the page, because only the components inside the actionRegion is processed by the server. Here's a simple example:

Controller

public with sharing class renderFile {
    public transient Blob fileBody { get; set; }
    public String contentType { get; set; }
    public String fileName { get; set; }
    public string[] items { get; set; }

    public renderFile() {
        items = new string[0];
    }

    public void save() {
        Document d = new Document(FolderId=UserInfo.getUserId(), Name=fileName, Body=fileBody, ContentType=contentType);
        insert d;
        items.add('Uploaded '+d.Name+' as ID '+d.Id);
    }
    public void reRender() {
        items.add('Item: '+(items.size()+1));
    }
}

Page

<apex:page controller="renderFile">
    <apex:form id="form">
        <apex:pageBlock >
            <apex:pageBlockButtons location="bottom">
                <apex:actionRegion id="area51" renderRegionOnly="false">
                    <apex:commandButton value="Something" reRender="form" action="{!reRender}"/>
                </apex:actionRegion>
                <apex:commandButton value="Save" action="{!save}"/>
            </apex:pageBlockButtons>
            <apex:pageBlockSection >
                <apex:repeat value="{!items}" var="value">
                    <apex:outputText >{!value}</apex:outputText>
                </apex:repeat>
                <apex:inputFile contentType="{!contentType}" fileName="{!fileName}" value="{!fileBody}" />
            </apex:pageBlockSection>
        </apex:pageBlock>
    </apex:form>
</apex:page>

Are you trying to send a value modified into your component to your controller ?

If so, check this:

1. You should set the action to call in your apex:commandButton
2. You should set the component attribute to an apex:inputField in order to sent it using an standard apex:form to the controller.
3. Instead that you could invoke your controller method by javascript directly by using @RemoteAction
4. Also, you should use the function JSENCODE to escape x = {!value};

This is an small sample of the last option:

 var x = {!JSENCODE(value)};

    Visualforce.remoting.Manager.invokeAction(
        '{!$RemoteAction.MyController.sentMyValue}', 
        x, 
        function(result, event){
            console.log(result);
        }, 
        {escape: true}
    );