Using the HttpServlet class to set a Java handler
You can define a Java handler by overriding the selected methods of the HttpServlet
Cloud Functions will automatically redirect each HTTP
request to your handler depending on the HTTP
method used to initiate the request. A GET
request, for instance, will be redirected to your handler's doGet
method, and POST
, to doPost
. For a redirect to be successful, these handler methods must exist, otherwise the function will return HTTP method XXX is not supported by this URL
with code 405
.
Unsupported methods
When using this model, please note that certain HttpServletRequest
HttpServletRequest
:
- getAuthType
- getCookies
- upgrade
- authenticate
- login
- logout
- getContextPath
- getServletPath
- getPathTranslated
- getRealPath
- getRemotePort
- getLocalAddr
- getLocalPort
- getServerPort
- isUserInRole
- getUserPrincipal
- getRequestedSessionId
- getSession
- changeSessionId
- isRequestedSessionIdValid
- isRequestedSessionIdFromCookie
- isRequestedSessionIdFromURL
- isRequestedSessionIdFromUrl
HttpServletResponse
:
- encodeURL
- encodeRedirectURL
- encodeUrl
- encodeRedirectUrl
Example of modeling various function behaviors when invoked using different HTTP methods
Warning
Do not use the ?integration=raw
parameter to invoke this function. If you do, the function will not get any data about the original request's methods, headers, or parameters.
Cloud Functions supports Maven, which is a dependency management system for Java
.
To create a function:
- Create a file named
Handler.java
at/src/main/java/Handler.java
and a file namedpom.xml
. - Add the
/src
directory and thepom.xml
file to a ZIP archive. - Upload the ZIP archive to Cloud Functions.
pom.xml
file:
<project>
<modelVersion>4.0.0</modelVersion>
<groupId>my.company.app</groupId>
<artifactId>servlet</artifactId>
<version>1</version>
<properties>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>compile</scope>
</dependency>
</dependencies>
</project>
Handler.java
file:
import java.io.IOException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class Handler extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
// by setting the Content-Type to text/html, we let the browser render the HTML code
response.setContentType("text/html");
// displayed in bold when the function is invoked from the browser
response.getOutputStream().print("<b>Hello, world. In bold.</b>");
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
var name = request.getParameter("name");
response.getWriter().println("Hello, " + name);
// the printWriter class returned by the getWriter method, make sure it's closed
response.getWriter().close();
}
}
Request examples:
GET
method:
<b>Hello, world. In bold.</b>
Note
Running a GET
request in a browser will display this string in bold without any tags because you had specified Content-Type: text/html
in your handler's code.
POST
method, name=Anonymous
as your request parameter:
Hello, Anonymous
PUT
method:
HTTP method PUT is not supported by this URL