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小编给大家分享一下Java中用表达式数调用的实例代码，希望大家阅读完这篇文章后大所收获，下面让我们一起去探讨吧！
利用表达式树构建委托改善反射性能 做了一点小更改正好适合自己用
public static class DynamicMethodBuilder
{public static Delegate BuildDynamicDelegate(MethodInfo methodInfo, ConstructorInfo constructorInfo = null)
{if (methodInfo == null)throw new ArgumentNullException("methodInfo");
List<ParameterExpression> paramExpressions = methodInfo.GetParameters().Select((p, i) =>{var name = "param" + (i + 1);return Expression.Parameter(p.ParameterType, name);
}).ToList();
MethodCallExpression callExpression;if (methodInfo.IsStatic)
{//Call(params....)callExpression = Expression.Call(methodInfo, paramExpressions);
}else{if (constructorInfo != null)
{//Instance(params).Call(params....)List<ParameterExpression> constructorParamExpressions = constructorInfo.GetParameters().Select((p, i) =>{var name = "constparam" + (i + 1);return Expression.Parameter(p.ParameterType, name);
}).ToList();
callExpression = Expression.Call(Expression.New(constructorInfo, constructorParamExpressions), methodInfo, paramExpressions);
paramExpressions.InsertRange(0, constructorParamExpressions);
}else{
callExpression = Expression.Call(Expression.New(methodInfo.ReflectedType), methodInfo, paramExpressions);
}
}return Expression.Lambda(callExpression, paramExpressions).Compile();
}
}测试：
public class Baby
{
private readonly DateTime _birthDay;
public Baby(DateTime birthDay)
{
_birthDay = birthDay;
}
public Baby()
{
_birthDay = DateTime.Now;
}
public string GetBabyInfo(string name, int sex) => $"姓名：{name} , 出生天数：{ DateTime.Now- _birthDay} ,性别 ：{(sex == 1 ? "男" : "女")}";
}
class Program
{
static void Main(string[] args)
{
Type targetType = Assembly.GetExecutingAssembly().GetType("ConsoleApplication1.Baby");
MethodInfo methodInfo = targetType.GetMethod("GetBabyInfo", new[] { typeof(string), typeof(int) });
ConstructorInfo constructor = targetType.GetConstructor(new[] { typeof(DateTime) });
WithConstructor(methodInfo, constructor);
WithOutConstructor(methodInfo);
Console.ReadKey();
}
static void WithConstructor(MethodInfo methodInfo, ConstructorInfo constructor)
{
var func = (Func<DateTime, string, int, string>)DynamicMethodBuilder.BuildDynamicDelegate(methodInfo, constructor);
Console.WriteLine(func(DateTime.Now.AddDays(-100), "糖墩儿", 1));
}
static void WithOutConstructor(MethodInfo methodInfo)
{
var func = (Func<string, int, string>)DynamicMethodBuilder.BuildDynamicDelegate(methodInfo);
Console.WriteLine(func("糖墩儿", 1));
}
}看完了这篇文章，相信你对Java中用表达式数调用的实例代码有了一定的了解，想了解更多相关知识，欢迎关注亿速云行业资讯频道，感谢各位的阅读！
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