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fix: optimize refresh logic to prevent redundant fetches #28

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mlopezFC wants to merge 2 commits into from
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fix: optimize refresh logic to prevent redundant fetches #28

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d4a1e5e
fix: optimize refresh logic to prevent redundant fetches
google-labs-jules[bot] May 24, 2025
20fd9b1
perf(RssItems): Implement debounced refresh to avoid breaking change
google-labs-jules[bot] May 26, 2025
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6 changes: 6 additions & 0 deletions pom.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -134,6 +134,12 @@
<version>4.13.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-core</artifactId>
<version>5.18.0</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.flowingcode.vaadin.addons.demo</groupId>
<artifactId>commons-demo</artifactId>
Expand Down
84 changes: 73 additions & 11 deletions src/main/java/com/flowingcode/vaadin/addons/rssitems/RssItems.java
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Original file line number Diff line number Diff line change
Expand Up @@ -34,8 +34,10 @@
import com.vaadin.flow.component.HasSize;
import com.vaadin.flow.component.HasStyle;
import com.vaadin.flow.component.Tag;
import com.vaadin.flow.component.UI;
import com.vaadin.flow.component.dependency.JsModule;
import com.vaadin.flow.component.dependency.NpmPackage;
import com.vaadin.flow.internal.StateTree.ExecutionRegistration;

/**
* Simple RSS Reader component based on https://github.com/TherapyChat/rss-items
Expand All @@ -54,7 +56,9 @@ public class RssItems extends Component implements HasSize, HasStyle {

private boolean extractImageFromDescription;

private static final String ERROR_RSS = "<rss>\r\n" +
private ExecutionRegistration pendingRefreshRegistration;

public static final String ERROR_RSS = "<rss>\r\n" +
" <channel>\r\n" +
" <item>\r\n" +
" <title>Error Retrieving RSS</title>\r\n" +
Expand All @@ -63,7 +67,7 @@ public class RssItems extends Component implements HasSize, HasStyle {
" <thumbnail url=\"https://\"></thumbnail>\r\n" +
" </item>";

private static final String IMAGE_METHOD = " $0._getItemImageScr = function (item) {\r\n" +
public static final String IMAGE_METHOD = " $0._getItemImageScr = function (item) {\r\n" +
" var element = document.createElement('div');\r\n" +
" element.innerHTML = item.%%ATTRIBUTE_NAME%%;\r\n" +
" var image = element.querySelector('img') || {};\r\n" +
Expand All @@ -72,11 +76,11 @@ public class RssItems extends Component implements HasSize, HasStyle {
"";


private static final int DEFAULT_MAX = Integer.MAX_VALUE;
public static final int DEFAULT_MAX = Integer.MAX_VALUE;

private static final int DEFAULT_MAX_TITLE_LENGTH = 50;
public static final int DEFAULT_MAX_TITLE_LENGTH = 50;

private static final int DEFAULT_MAX_EXCERPT_LENGTH = 100;
public static final int DEFAULT_MAX_EXCERPT_LENGTH = 100;

/**
* @param url rss feed url
Expand All @@ -102,7 +106,6 @@ public RssItems(String url, int max, int maxTitleLength, int maxExcerptLength, b
this.setMaxTitleLength(maxTitleLength);
addClassName("x-scope");
addClassName("rss-items-0");
refreshUrl();
}

/**
Expand All @@ -112,7 +115,49 @@ public RssItems(String url) {
this(url,DEFAULT_MAX, DEFAULT_MAX_TITLE_LENGTH, DEFAULT_MAX_EXCERPT_LENGTH, false);
}

/**
* Constructor for testing purposes.
*/
protected RssItems() {
}

private void scheduleRefresh() {
UI ui = UI.getCurrent();
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@javier-godoy javier-godoy May 26, 2025

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  • The check is not where there is a current UI, but whether the component is attached (refreshUrl calls invokeXmlToItems which calls this.getElement().executeJs which requires the element to be attached).
  • If the component is not attached, scheduleRefresh will do nothing.
  • Call scheduleRefresh on attach.

if (ui == null) {
// If no UI is available (e.g., background thread or testing without proper UI setup),
// consider an immediate refresh or log a warning.
// For now, let's do an immediate refresh as a fallback,
// though this might not be ideal in all detached scenarios.
// This matches the original behavior more closely if UI isn't available.
refreshUrl();
return;
}

// If there's a pending registration, remove it.
if (pendingRefreshRegistration != null) {
try {
pendingRefreshRegistration.remove();
} catch (Exception e) {
// Log or handle potential exceptions if .remove() fails, though typically it shouldn't.
// For example, if the registration is already inactive.
System.err.println("Error removing pending refresh registration: " + e.getMessage());
}
pendingRefreshRegistration = null;
}

// Schedule refreshUrl to be called before the client response.
// The lambda uiParam -> refreshUrl() is used because the consumer takes the UI as a parameter.
pendingRefreshRegistration = ui.beforeClientResponse(this, uiParam -> refreshUrl());
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@javier-godoy javier-godoy May 26, 2025

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Schedule in the UI to which the component is attached.

}

private void refreshUrl() {
if (pendingRefreshRegistration != null) {
// If refreshUrl is called directly while a refresh was scheduled,
// the scheduled one is now effectively preempted or redundant.
// We nullify the registration to reflect this.
// Note: We don't call .remove() here as this method IS the execution (or a direct call).
pendingRefreshRegistration = null;
}
try {
String rss = obtainRss(url);
invokeXmlToItems(rss);
Expand All @@ -126,7 +171,7 @@ private void invokeXmlToItems(String rss) {
this.getElement().executeJs("this.xmlToItems($0)", rss);
}

private String obtainRss(String url) throws ClientProtocolException, IOException {
protected String obtainRss(String url) throws ClientProtocolException, IOException {
HttpClient client = HttpClientBuilder.create().build();
HttpGet request = new HttpGet(URI.create(url));
request.addHeader("Content-Type", "application/xml");
Expand Down Expand Up @@ -155,7 +200,7 @@ public void setAuto(boolean auto) {
*/
public void setMaxTitleLength(int length) {
this.getElement().setProperty("maxTitleLength", length);
refreshUrl();
scheduleRefresh();
}

/**
Expand All @@ -164,7 +209,7 @@ public void setMaxTitleLength(int length) {
*/
public void setMaxExcerptLength(int length) {
this.getElement().setProperty("maxExcerptLength", length);
refreshUrl();
scheduleRefresh();
}

/**
Expand All @@ -173,12 +218,12 @@ public void setMaxExcerptLength(int length) {
*/
public void setMax(int max) {
this.getElement().setProperty("max", max);
refreshUrl();
scheduleRefresh();
}

public void setExtractImageFromDescription(boolean extractImageFromDescription) {
this.extractImageFromDescription = extractImageFromDescription;
refreshUrl();
scheduleRefresh();
}

/**
Expand All @@ -188,6 +233,23 @@ public void setExtractImageFromDescription(boolean extractImageFromDescription)
public void setUrl(String url) {
this.getElement().setProperty("url", url);
this.url = url;
scheduleRefresh();
}

/**
* Refreshes the RSS feed.
*/
public void refresh() {
if (pendingRefreshRegistration != null) {
try {
pendingRefreshRegistration.remove();
} catch (Exception e) {
// Log or handle potential exceptions.
System.err.println("Error removing pending refresh registration during manual refresh: " + e.getMessage());
}
pendingRefreshRegistration = null;
}
refreshUrl();
}

}
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