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Notes on Java

Last updated: 2022-01-27 11:27:15

    Code Format

    The code form of a SCF function developed in Java is generally as follows:

    package example;
    public class Hello {
       public String mainHandler(KeyValueClass kv) {
           System.out.println("Hello world!");
           System.out.println(String.format("key1 = %s", kv.getKey1()));
           System.out.println(String.format("key2 = %s", kv.getKey2()));
           return String.format("Hello World");

    Create the parameter KeyValueClass class:

    package example;
    public class KeyValueClass {
       String key1;
       String key2;
       public String getKey1() {
           return this.key1;
       public void setKey1(String key1) {
           this.key1 = key1;
       public String getKey2() {
           return this.key2;
       public void setKey2(String key2) {
           this.key2 = key2;
       public KeyValueClass() {

    Execution Method

    As Java has the concept of package, its execution method is different from other languages and requires package information. The corresponding execution method in the code example is example.Hello::mainHandler, where example is identified as the Java package, Hello the class, and mainHandler the class method.

    Input Parameters and Returns

    In the sample code, the input parameters used by mainHandler have two types: String and Context, and the return is in String type. The former type of the input parameters identifies the event input parameter, while the latter the function runtime information. Currently, types supported for event input parameters and function returns include Java base types and POJO type; the function runtime is currently in com.qcloud.scf.runtime.Context type, and its associated library files can be downloaded here.

    • Types supported for event input and return parameters
      • Java base types, including eight basic types and wrapper classes (byte, int, short, long, float, double, char, and boolen) and String type.
      • POJO (Plain Old Java Object) type. You should use variable POJOs and public getters and setters to provide implementations of the corresponding types in the code.
    • Context input parameters
      • To use Context, you need to use com.qcloud.scf.runtime.Context; in the code to import the package and include the jar package when it is packaged.
      • If this object is not used, you can ignore it in the function input parameters, which can be written as public String mainHandler(String name).

    The event structures of input parameters passed in by certain triggers have been defined and can be used directly. You can get and use the Java libraries through the Cloud Event Definition. If you have any questions during use, you can submit an issue or ticket for assistance.

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