Simply Expression Language

📖 English Documentation | 📖 Chinese Documentation

Introduction

Simply Expression Language (SEL) aims to simplify repetitive coding tasks involving judgment, computation, value extraction, and structural transformation.
Primary application scenarios: Dynamic rule evaluation, type adaptation (message conversion), and dynamic computation with scheduling/process engines.

Environment & Dependencies

• JDK 1.8+ • fastjson2 2.0.56+ • slf4j 1.7.30+

Features

• Hierarchical Structure Support: Easily manipulate/transform JSON, POJOs, etc.
• Null-safe Access: Eliminate tedious null checks
• Branch Logic: Supports complex compound statements, if-else/for loops
• Method Invocation: Directly call object methods and custom utility functions
• Ease of Use: Compute native objects directly via API without building context objects

Dependency Configuration

Due to domain renewal issues, new versions use the net domain.

New Versions (Post 1.1.1)

<dependency>
    <groupId>net.fanjr.simplify</groupId>
    <artifactId>simplify-el</artifactId>
    <version>1.3.1</version>
</dependency>

Legacy Versions (Pre 1.1.0)

<dependency>
    <groupId>org.fanjr.simplify</groupId>
    <artifactId>simplify-el</artifactId>
    <version>1.1.0</version>
</dependency>

Documentation

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Click Here for detailed documentation
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Key Capabilities

• Basic expression evaluation, placeholder substitution, arithmetic operations, regex matching • Assignment operations, type casting (supports JSON conversion scenarios) • Complex statement composition • Java method invocation and custom functions • Conditional branching, ternary expressions, loops

Expression Examples

// Basic example
boolean result = ELExecutor.eval(
        "a==100",
        "{'a':100}",
        boolean.class);
Assertions.assertTrue(result);

// Arithmetic operations
int result = ELExecutor.eval("2 * a - (b + c) * d", "{'a':1,'b':2,'c':3,'d':4}", int.class);
// 2*1-(2+3)*4 = -18
Assertions.assertEquals(-18, result);

// Assignment & computation
Map<String, Object> context = new HashMap<>();
context.put("val", 10);
ELExecutor.eval("a=10;val=val+1;val++;result=a+val;", context);
Assertions.assertEquals(10, ElUtils.cast(context.get("a"), int.class));
Assertions.assertEquals(12, ElUtils.cast(context.get("val"), int.class));
Assertions.assertEquals(22, ElUtils.cast(context.get("result"), int.class));

// Assign POJO property via expression
TestReq req = new TestReq();
ELExecutor.eval("head.serialId='123456'", req);
System.out.println(req.getHead().getSerialId());

// Call Java methods
Map<String, Object> context = new HashMap<>();
context.put("val", "010");
// Convert string "010" to int, call toString().length()
Assertions.assertEquals(2, ELExecutor.eval("((int)val).toString().length()", context, int.class));

Ternary Expressions

Map<String, Object> context = new HashMap<>();
context.put("flag", 100);
context.put("val", 10);
Assertions.assertEquals(100, ELExecutor.eval("flag>=100?val*10:val/10", context, int.class));
Assertions.assertEquals(1, ELExecutor.eval("flag<100?val*10:val/10", context, int.class));

If-Else Branching

Map<String, Object> context = new HashMap<>();

// Branch 1 (IF)
context.put("flag", 1);
ELExecutor.eval("if(flag==1){\n a=1;\n }", context);
Assertions.assertEquals(1, ElUtils.cast(context.get("a"), int.class));
context.clear();

// Branch 2 (IF-ELSE-IF)
context.put("flag", 2);
ELExecutor.eval("if(flag==1){a=1; }else if(flag==2){ a=2;a++; }", context);
Assertions.assertEquals(3, ElUtils.cast(context.get("a"), int.class));
context.clear();

// Branch 3 (IF-ELSE-IF-ELSE)
context.put("flag", 3);
ELExecutor.eval("if(flag==1){\n a=1;\n }else if(flag==2){ a=2;a++; }else{ a=0; }", context);
Assertions.assertEquals(0, ElUtils.cast(context.get("a"), int.class));

For Loops

// Control group: Java loop
int[] arr = new int[10];
for (int i = 0; i < 10; i++) {
    arr[i] = 3 * (i + 1234) - i;
}

// C-style loop
Map<String, Object> context = new HashMap<>();
ELExecutor.eval("for(i=0;i<10;i++){arr[i]=3 * (i + 1234) - i}", context);
Assertions.assertArrayEquals(arr, ElUtils.cast(context.get("arr"), int[].class));
context.clear();

// Iterator-style loop
context.put("num", new int[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9});
ELExecutor.eval("for(i:num){arr[i]=3 * (i + 1234) - i}", context);
Assertions.assertArrayEquals(arr, ElUtils.cast(context.get("arr"), int[].class));
context.clear();

// Numeric loop (equivalent to i=0;i<10;i++)
ELExecutor.eval("for(i:10){arr[i]=3 * (i + 1234) - i}", context);
Assertions.assertArrayEquals(arr, ElUtils.cast(context.get("arr"), int[].class));

// Nested loops (print 9x9 multiplication table)
ELExecutor.eval("for(i=1;i<=9;i++){" +
        "   for(j=1;j<=9;j++){" +
        "       $.printf(i+'*'+j+'='+(i*j)+'\t');" +
        "   }" +
        "   $.printf('\n')" +
        "}", new HashMap<>());

Custom & Built-in Functions

Custom Function Extension

# Create META-INF/simplify-el.functions
$=net.fanjr.simplify.el.InnerFunctions

Sample inner functions (InnerFunctions):

public class InnerFunctions {
    @ELMethod(order = Integer.MAX_VALUE)
    public static void println(Object object) {
        System.out.println(object);
    }
}

Built-in Functions

• $.println(xxxx): Print to console • $.printf(xxxx): Print without newline • $.log(xxxx): Log using SLF4J • $.max(a,b): Return larger value • $.min(a,b): Return smaller value • $.merge([map1,map2...]): Deep merge maps • $.getEnumMap(xx): Get enum mapping

Roadmap

• Analyze Java standard libraries for common method integration • Optimize usability with additional utility classes • Improve documentation and error handling

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