heartlhj / go-expression

GO语言EL表达式

expression EL表达式

Install

go get github.com/heartlhj/go-expression

功能

• 字符串的提取和比较

    context := spel.StandardEvaluationContext{}
    m := make(map[string]interface{})
    m["name"] = "lisi"
    m["age"] = 18
    context.SetVariables(m)
    parser := SpelExpressionParser{}
    expressionString := "#name=='lisi'"
    //expressionString := "#name" //返回lisi
    valueContext := parser.ParseExpression(expressionString).GetValueContext(&context)

• 数字比较，支持int和 float64

    context := spel.StandardEvaluationContext{}
    m := make(map[string]interface{})
    m["name"] = "lisi"
    m["age"] = 18
    context.SetVariables(m)
    parser := SpelExpressionParser{}
    expressionString := "#age>=10"
    valueContext := parser.ParseExpression(expressionString).GetValueContext(&context)

float64比较

    context := spel.StandardEvaluationContext{}
    m := make(map[string]interface{})
    var ageFloat float64
    ageFloat = 10
    m["num"] = ageFloat
    context.SetVariables(m)
    parser := SpelExpressionParser{}
    expressionString := "#num>=9f"
    valueContext := parser.ParseExpression(expressionString).GetValueContext(&context)

• 与（&&）或 （||）操作

    context := spel.StandardEvaluationContext{}
    m := make(map[string]interface{})
    m["name"] = "lisi"
    m["age"] = 18
    context.SetVariables(m)
    parser := SpelExpressionParser{}
    expressionString := "#name=='lisi' && #age>=3"
    valueContext := parser.ParseExpression(expressionString).GetValueContext(&context)

• 复合结构，迭代提取

    context := spel.StandardEvaluationContext{}
    context.AddPropertyAccessor(spel.MapAccessor{})
    m := make(map[string]interface{})
    m["name"] = "lisi"
    m["age"] = 18
    m1 := make(map[string]interface{})
    m2 := make(map[string]interface{})
    m2["num"] = 12
    m1["code"] = m2
    m["order"] = m1
    context.SetVariables(m)
    parser := SpelExpressionParser{}
    expressionString := "#order.code.num==12"
    valueContext := parser.ParseExpression(expressionString).GetValueContext(&context)

• 数组和切片提取

    context := spel.StandardEvaluationContext{}
    context.AddPropertyAccessor(spel.MapAccessor{})
    m := make(map[string]interface{})
    m["name"] = "lisi"
    m["age"] = 18
    m1 := make(map[string]interface{})
    //切片
    //orders := make([]Order, 2)
    //数组
    orders := [2]Order{}
    orders[0] = Order{name: "lisi", age: 12}
    orders[1] = Order{name: "wang", age: 24}
    m1["code"] = orders
    m["order"] = m1
    context.SetVariables(m)
    parser := SpelExpressionParser{}
    expressionString := "#order.code[0].name=='lisi'"
    valueContext := parser.ParseExpression(expressionString).GetValueContext(&context)

• 字符串下标判断提取

    context := spel.StandardEvaluationContext{}
    context.AddPropertyAccessor(spel.MapAccessor{})
    m := make(map[string]interface{})
    m["name"] = "lisi"
    m["age"] = 18
    context.SetVariables(m)
    parser := SpelExpressionParser{}
    expressionString := "#name[2]=='i'"
    valueContext := parser.ParseExpression(expressionString).GetValueContext(&context)

go-expression's Issues

请问支持方法调用或者用户定义的函数吗

类似 Spring EL 的方式：

ExpressionParser parser = new SpelExpressionParser();
Expression exp = parser.parseExpression("'Hello World'.concat('!')");
String message = (String) exp.getValue();

大于(>)、小于(<)操作符被识别为大于等于(>=)、小于等于(<=)

context := spel.StandardEvaluationContext{}
m := make(map[string]interface{})
m["name"] = "lisi"
m["age"] = 18
context.SetVariables(m)
parser := expression.SpelExpressionParser{}
expressionString := "#age>18"
valueContext := parser.ParseExpression(expressionString).GetValueContext(&context)

// 结果打印为true
fmt.Println(valueContext)

貌似是这里Tokenizer中调用pushCharToken，放入的是一个 大于等于的算子

case ">":
if t.isTwoCharToken(TokenKind{TokenKindType: GE, TokenChars: []rune(GE), HasPayload: len([]rune(GE)) == 0}) {
	t.pushPairToken(TokenKind{TokenKindType: GE, TokenChars: []rune(GE), HasPayload: len([]rune(GE)) == 0})
} else {
	t.pushCharToken(TokenKind{TokenKindType: GE, TokenChars: []rune(GE), HasPayload: len([]rune(GE)) == 0})
}
break

在 InternalSpelExpressionParser的eatRelationalExpression方法中：

// 这里似乎有意把 > 当做 >=， < 当做 <= 处理，不知何意
if kindType == GT {
    eq := OpGE{Operator: &operator}
    return &eq, nil
}
if kindType == LT {
  eq := OpLE{Operator: &operator}
  return &eq, nil
}

不太能够理解作者的意图

EL 表达式或操作不行

context := spel.StandardEvaluationContext{} m := make(map[string]interface{}) m["create_user"] = "wsq_uid1" m["role_id"] = 1 m["money"] = 10000 m["things_num"] = 12 m["age"] = 18 context.SetVariables(m) parser := SpelExpressionParser{} expressionString := "#create_user=='lisi' || #age>=3" valueContext := parser.ParseExpression(expressionString).GetValueContext(&context) fmt.Println("结果为：", valueContext)

float64 类型的比较不生效

context := spel.StandardEvaluationContext{}
m := make(map[string]interface{})
    var ageFloat float64
ageFloat = 8.12
m["num"] = ageFloat
		context.SetVariables(m)
		parser := expression.SpelExpressionParser{}
		expressionString := "#num>=9f"
		valueContext := parser.ParseExpression(expressionString).GetValueContext(&context)
		So(valueContext, ShouldBeFalse)