335 lines
12 KiB
Plaintext
335 lines
12 KiB
Plaintext
:toc:
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= Custom Syntax Elements
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This section systematically outlines the interfaces and capabilities in QLExpress4 for customizing syntax elements.
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== Overview
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* Custom functions
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** Implement the CustomFunction interface
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** Use Java functional interfaces
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** Register via annotation scanning
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** Add via QLExpress script
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** Implement QLFunctionalVarargs
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* Custom operators
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** Implement CustomBinaryOperator
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** Replace built-in operators
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** Use Java functional interfaces
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** Add aliases
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** Implement QLFunctionalVarargs
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* Extension functions
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** Extend ExtensionFunction
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** Implement QLFunctionalVarargs
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* Aliases for operators and functions
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== Custom Functions
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=== Implement the CustomFunction interface
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[source,java,indent=0]
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----
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package com.alibaba.qlexpress4.test.function;
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import com.alibaba.qlexpress4.runtime.Parameters;
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import com.alibaba.qlexpress4.runtime.QContext;
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import com.alibaba.qlexpress4.runtime.function.CustomFunction;
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public class HelloFunction implements CustomFunction {
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@Override
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public Object call(QContext qContext, Parameters parameters)
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throws Throwable {
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String tenant = (String)qContext.attachment().get("tenant");
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return "hello," + tenant;
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}
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}
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----
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[source,java,indent=0]
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----
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Express4Runner express4Runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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express4Runner.addFunction("hello", new HelloFunction());
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String resultJack = (String)express4Runner.execute("hello()",
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Collections.emptyMap(),
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// Additional information(tenant for example) can be brought into the custom function from outside via attachments
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QLOptions.builder().attachments(Collections.singletonMap("tenant", "jack")).build()).getResult();
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assertEquals("hello,jack", resultJack);
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String resultLucy =
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(String)express4Runner
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.execute("hello()",
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Collections.emptyMap(),
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QLOptions.builder().attachments(Collections.singletonMap("tenant", "lucy")).build())
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.getResult();
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assertEquals("hello,lucy", resultLucy);
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----
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=== Use Java functional interfaces
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[source,java,indent=0]
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----
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Express4Runner runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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// Function<T,R>
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runner.addFunction("inc", (Function<Integer, Integer>)x -> x + 1);
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// Predicate<T>
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runner.addFunction("isPos", (Predicate<Integer>)x -> x > 0);
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// Runnable
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runner.addFunction("notify", () -> {
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});
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// Consumer<T>
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runner.addFunction("print", (Consumer<Object>)System.out::println);
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Object r1 = runner.execute("inc(1)", Collections.emptyMap(), QLOptions.DEFAULT_OPTIONS).getResult();
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Object r2 = runner.execute("isPos(1)", Collections.emptyMap(), QLOptions.DEFAULT_OPTIONS).getResult();
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assertEquals(2, r1);
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assertEquals(true, r2);
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----
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=== Register via annotations
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[source,java,indent=0]
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----
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public static class MyFunctionUtil {
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@QLFunction({"myAdd", "iAdd"})
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public int add(int a, int b) {
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return a + b;
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}
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@QLFunction("arr3")
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public static int[] array3(int a, int b, int c) {
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return new int[] {a, b, c};
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}
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@QLFunction("concat")
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public String concat(String a, String b) {
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return a + b;
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}
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}
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----
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[source,java,indent=0]
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----
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Express4Runner express4Runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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BatchAddFunctionResult addResult = express4Runner.addObjFunction(new MyFunctionUtil());
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assertEquals(4, addResult.getSucc().size());
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Object result =
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express4Runner.execute("myAdd(1,2) + iAdd(5,6)", new HashMap<>(), QLOptions.DEFAULT_OPTIONS).getResult();
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assertEquals(14, result);
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express4Runner.addStaticFunction(MyFunctionUtil.class);
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Object result1 =
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express4Runner.execute("arr3(5,9,10)[2]", new HashMap<>(), QLOptions.DEFAULT_OPTIONS).getResult();
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assertEquals(10, result1);
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Object result2 =
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express4Runner.execute("concat('aa', null)", new HashMap<>(), QLOptions.DEFAULT_OPTIONS).getResult();
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assertEquals("aanull", result2);
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----
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=== Add via QLExpress script
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[source,java,indent=0]
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----
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public static class JoinFunction implements QLFunctionalVarargs {
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@Override
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public Object call(Object... params) {
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return Arrays.stream(params).map(Object::toString).collect(Collectors.joining(","));
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}
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}
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----
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=== Implement QLFunctionalVarargs
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[source,java,indent=0]
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----
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Express4Runner express4Runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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express4Runner.addVarArgsFunction("join", new JoinFunction());
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Object resultFunction =
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express4Runner.execute("join(1,2,3)", Collections.emptyMap(), QLOptions.DEFAULT_OPTIONS).getResult();
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assertEquals("1,2,3", resultFunction);
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----
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[source,java,indent=0]
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----
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Express4Runner express4Runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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express4Runner.addVarArgsFunction("join", new JoinFunction());
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Object resultFunction =
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express4Runner.execute("join(1,2,3)", Collections.emptyMap(), QLOptions.DEFAULT_OPTIONS).getResult();
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assertEquals("1,2,3", resultFunction);
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----
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== Custom Operators
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=== Implement CustomBinaryOperator and set precedence
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[source,java,indent=0]
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----
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Express4Runner runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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runner.addOperator("?><", (left, right) -> left.get().toString() + right.get().toString(), QLPrecedences.ADD);
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Object r = runner.execute("1 ?>< 2 * 3", new HashMap<>(), QLOptions.DEFAULT_OPTIONS).getResult();
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// precedence set to ADD, so multiply first, then custom operator: "1" + "6" => "16"
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assertEquals("16", r);
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----
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=== Replace built-in operators
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[source,java,indent=0]
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----
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Express4Runner runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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boolean ok = runner.replaceDefaultOperator("+",
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(left, right) -> Double.parseDouble(left.get().toString()) + Double.parseDouble(right.get().toString()));
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assertTrue(ok);
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Object r = runner.execute("'1.2' + '2.3'", Collections.emptyMap(), QLOptions.DEFAULT_OPTIONS).getResult();
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assertEquals(3.5d, r);
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----
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=== Use Java functional interfaces
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[source,java,indent=0]
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----
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Express4Runner express4Runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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express4Runner.addOperatorBiFunction("join", (left, right) -> left + "," + right);
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Object resultOperator =
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express4Runner.execute("1 join 2 join 3", Collections.emptyMap(), QLOptions.DEFAULT_OPTIONS).getResult();
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assertEquals("1,2,3", resultOperator);
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----
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=== Implement QLFunctionalVarargs
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[source,java,indent=0]
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----
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Express4Runner runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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runner.addOperator("join", params -> params[0] + "," + params[1]);
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Object r = runner.execute("1 join 2", Collections.emptyMap(), QLOptions.DEFAULT_OPTIONS).getResult();
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assertEquals("1,2", r);
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----
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== Extension Functions
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=== Extend ExtensionFunction
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[source,java,indent=0]
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----
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ExtensionFunction helloFunction = new ExtensionFunction() {
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@Override
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public Class<?>[] getParameterTypes() {
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return new Class[0];
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}
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@Override
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public String getName() {
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return "hello";
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}
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@Override
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public Class<?> getDeclaringClass() {
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return String.class;
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}
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@Override
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public Object invoke(Object obj, Object[] args) {
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String originStr = (String)obj;
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return "Hello," + originStr;
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}
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};
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Express4Runner express4Runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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express4Runner.addExtendFunction(helloFunction);
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Object result =
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express4Runner.execute("'jack'.hello()", Collections.emptyMap(), QLOptions.DEFAULT_OPTIONS).getResult();
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assertEquals("Hello,jack", result);
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----
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=== Implement QLFunctionalVarargs
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[source,java,indent=0]
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----
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// simpler way to define extension function
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express4Runner.addExtendFunction("add",
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Number.class,
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params -> ((Number)params[0]).intValue() + ((Number)params[1]).intValue());
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QLResult resultAdd = express4Runner.execute("1.add(2)", Collections.emptyMap(), QLOptions.DEFAULT_OPTIONS);
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assertEquals(3, resultAdd.getResult());
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----
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== QLFunctionalVarargs: One object defines three kinds of operations
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The same QLFunctionalVarargs object can serve as the implementation of a function, an operator, and an extension function at the same time, making it easy to reuse unified semantics and implementation across multiple places. This capability comes from the interface’s varargs design; see the example and interface definition below. For background discussion, refer to link:https://github.com/alibaba/QLExpress/issues/407[issue407]:
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[source,java,indent=0]
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----
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Express4Runner runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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QLFunctionalVarargs allInOne = params -> {
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// sum numbers no matter how many args
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double sum = 0d;
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for (Object p : params) {
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if (p instanceof Number) {
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sum += ((Number)p).doubleValue();
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}
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}
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return sum;
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};
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// as function
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runner.addVarArgsFunction("sumAll", allInOne);
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// as operator
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runner.addOperator("+&", allInOne);
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// as extension function: first arg is the receiver, followed by call arguments
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runner.addExtendFunction("plusAll", Number.class, allInOne);
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Map<String, Object> ctx = new HashMap<>();
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Object rf = runner.execute("sumAll(1,2,3)", ctx, QLOptions.DEFAULT_OPTIONS).getResult();
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Object ro = runner.execute("1 +& 4", ctx, QLOptions.DEFAULT_OPTIONS).getResult();
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Object re = runner.execute("1.plusAll(5)", ctx, QLOptions.DEFAULT_OPTIONS).getResult();
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assertEquals(6d, rf);
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assertEquals(5d, ro);
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assertEquals(6d, re);
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----
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=== Interface definition
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[source,java,indent=0]
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----
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package com.alibaba.qlexpress4.api;
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/**
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* Author: TaoKan
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*/
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@FunctionalInterface
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public interface QLFunctionalVarargs {
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Object call(Object... params);
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}
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----
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== Aliases for operators and functions (keyword aliases also supported)
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[source,java,indent=0]
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----
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Express4Runner express4Runner = new Express4Runner(InitOptions.DEFAULT_OPTIONS);
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// add custom function zero
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express4Runner.addFunction("zero", (String ignore) -> 0);
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// keyword alias
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assertTrue(express4Runner.addAlias("如果", "if"));
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assertTrue(express4Runner.addAlias("则", "then"));
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assertTrue(express4Runner.addAlias("否则", "else"));
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assertTrue(express4Runner.addAlias("返回", "return"));
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// operator alias
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assertTrue(express4Runner.addAlias("大于", ">"));
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// function alias
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assertTrue(express4Runner.addAlias("零", "zero"));
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Map<String, Object> context = new HashMap<>();
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context.put("语文", 90);
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context.put("数学", 90);
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context.put("英语", 90);
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Object result = express4Runner
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.execute("如果 (语文 + 数学 + 英语 大于 270) 则 {返回 1;} 否则 {返回 零();}", context, QLOptions.DEFAULT_OPTIONS)
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.getResult();
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assertEquals(0, result);
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----
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== Notes and recommendations
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- Under the QLFunctionalVarargs calling convention, when invoking an extension function the first actual argument is the receiver object, followed by the call arguments; functions and operators do not include a receiver.
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- Set the precedence of custom operators according to the intended expression semantics to avoid confusion with existing rules.
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- Annotation-based registration only processes public methods, and duplicate names will fail to register; the batch registration result contains both success and failure lists.
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