dynamic variable: 比如说我想用variable "varA". The word "varA" retrieved from database, how can I use this word to get the variable value? 我现在想的是建一个lookup. dynamic functions: 比如说我想trim一个variable. The word ".trim()" retrieved from database, "" will be replaced by real variable and ".trim()" will be excuted, how can I do that? Thanks
g*g
3 楼
Java Reflection
be
【在 B*****g 的大作中提到】 : dynamic variable: : 比如说我想用variable "varA". The word "varA" retrieved from database, how : can I use this word to get the variable value? 我现在想的是建一个lookup. : dynamic functions: : 比如说我想trim一个variable. The word ".trim()" retrieved from : database, "" will be replaced by real variable and ".trim()" will be : excuted, how can I do that? : Thanks
A*o
4 楼
How about the scripting ability added since JDK 6? It might work here, too. But i have no experience on it.
c*t
5 楼
It is nothing more than an equivalent of BSF framework.
.
【在 A**o 的大作中提到】 : How about the scripting ability added since JDK 6? It might work here, too. : But i have no experience on it.
s*e
6 楼
How can you do it in java reflection? I am not sure if you can do it in a pure java way with java 1.6 scripting engine either. For either way, it will be interesting to see a working example.
c*t
7 楼
LZ is not concrete enough. So there won't be concrete example either :P
【在 s******e 的大作中提到】 : How can you do it in java reflection? : I am not sure if you can do it in a pure java way with java 1.6 scripting : engine either. : For either way, it will be interesting to see a working example.
s*e
8 楼
not concrete enough? I believe that even the poster title is good enough for you to come with a sample. The dynamic variable and dynamic functions are common features in emacscript based language such as .js and .as but it is extemely hard to any strong typed object oriented language. personally i do not see any way you can do it in java reflection. even with jsr223, you might still have a trouble to do it.
g*g
9 楼
Think of Spring IoC declared in XML. You declare a class name, a method name, and you can invoke the method. Something like Class c = Class.forName(yourClassName); Object o = c.newInstance(); Method method = c.getDeclaredMethod(yourMethod); method.invoke(o); You probably want to have a constructor passing in a String parameter, something we've seen in spring IoC too. I believe OP's problem can be resolved in a similar way, although he may need to format his string in DB with more type details
【在 s******e 的大作中提到】 : not concrete enough? : I believe that even the poster title is good enough for you to come with a : sample. : The dynamic variable and dynamic functions are common features in emacscript : based language such as .js and .as but it is extemely hard to any strong : typed object oriented language. personally i do not see any way you can do : it in java reflection. even with jsr223, : you might still have a trouble to do it.
s*e
10 楼
You misunderstood what dynamic variable and dynamic functions mean. they are not someting that preexist at the compiling time. both js ans as allow you to define a new memeber of class on the fly. .for example, adding a new variable/function to a class at run time.
g*g
11 楼
How you want to coin the names is not that important. The OP wants to call some function by parsing a string from DB. And Spring IoC is a perfect example for that. If you want to add new variable/function, look at AspectJ.
are
【在 s******e 的大作中提到】 : You misunderstood what dynamic variable and dynamic functions mean. they are : not someting that preexist at the compiling time. : both js ans as allow you to define a new memeber of class on the fly. : .for example, adding a new variable/function to a class at run time.
m*t
12 楼
I would go with an embedded scripting language too. Groovy or jruby are both good choices here, as they closely resemble java syntax.
【在 c*****t 的大作中提到】 : It is nothing more than an equivalent of BSF framework. : : .
F*n
13 楼
Mozilla Rhino Javascript. You can hack into it quite deep.
【在 m******t 的大作中提到】 : : I would go with an embedded scripting language too. : Groovy or jruby are both good choices here, as they closely : resemble java syntax.
c*t
14 楼
BeanShell is actually even better :P Zero learning curves.
【在 m******t 的大作中提到】 : : I would go with an embedded scripting language too. : Groovy or jruby are both good choices here, as they closely : resemble java syntax.
c*t
15 楼
Well, he wasn't specific enough in what he was trying to do. When he mentions "dynamic variable", it makes me wonder why and where he would use it.
emacscript
【在 s******e 的大作中提到】 : not concrete enough? : I believe that even the poster title is good enough for you to come with a : sample. : The dynamic variable and dynamic functions are common features in emacscript : based language such as .js and .as but it is extemely hard to any strong : typed object oriented language. personally i do not see any way you can do : it in java reflection. even with jsr223, : you might still have a trouble to do it.
s*e
16 楼
Even many terms are vague in cs. But these two are not vague at all when we talk about language. actually they are one of the criteria to distinguish a type strong langauge and a dynamic language. aspectj by nature is just another layer of compilation. actually no aop has ever brought dynamic variable and dynamic functions to the table. dynamic variable and fuctions are very useful when you do not know what and how many things you want your object to carry at compilation time.
m*i
17 楼
It should be something like eval() in python. did a little search, https:// eval.dev.java.net/ might be helpful.
be
【在 B*****g 的大作中提到】 : dynamic variable: : 比如说我想用variable "varA". The word "varA" retrieved from database, how : can I use this word to get the variable value? 我现在想的是建一个lookup. : dynamic functions: : 比如说我想trim一个variable. The word ".trim()" retrieved from : database, "" will be replaced by real variable and ".trim()" will be : excuted, how can I do that? : Thanks
m*t
18 楼
Very true. I used to use a lot of beanshell, even embedding it in a web app as an admin console. The active development on it seems to have stopped though.
【在 c*****t 的大作中提到】 : BeanShell is actually even better :P Zero learning curves.
m*t
19 楼
There is this design approach to implement validation logic in javascript, and run it once on client side, then again on server side with rhino. Very interesting idea, I thought.
【在 F****n 的大作中提到】 : Mozilla Rhino Javascript. You can hack into it quite deep.
c*t
20 楼
Why do you need "active" development anyways? It has already fullfilled its purposes.
【在 m******t 的大作中提到】 : : There is this design approach to implement validation : logic in javascript, and run it once on client side, then again : on server side with rhino. Very interesting idea, I thought.
m*t
21 楼
I personally don't have problems with that. I'm just saying that it might be a concern for some projects, especially when the latest version released is nominally a beta.
【在 c*****t 的大作中提到】 : Why do you need "active" development anyways? It has already fullfilled : its purposes.
B*g
22 楼
sorry，太忙没时间搞。这个是我前一段问的dynamic ETL map要用的。 parse source file没啥问题，map to target(oracle db)有问题。 假设source是 FixedLength firstname text 10
f + l is just an example. Real world can be complicate. Like first remove special characters from f and l, then trim them, then get first 20 characters, then trim again, then uppercase. More complicate example may involve if/else
You must first know what the expression language is. If you don't know, then there's no solution.
get
【在 B*****g 的大作中提到】 : f + l is just an example. : Real world can be complicate. : Like first remove special characters from f and l, then trim them, then get : first 20 characters, then trim again, then uppercase. : More complicate example may involve if/else
s******e 发帖数: 493
32
if so, even dynamic functions are not enough. Dynamic functions are not real dynamic, you still need to code them in your code base. what you need is either using db or xml file or any format file to act as a configuration file, treating your first name as operand one, and last name as operand two (if you are sure that you will only have two operands, and they will be stored in columns that you know ahead. Otherwise if even the operands are unknown at compilation time, it will be way too compli
s******e 发帖数: 493
33
just have thought, you may be able to take advantage of jdk 1.6 with mozilla rhino(the only built-in Jscript implemntation support in hotspot) for example you have a formula (op1 * 13 - op2)/13 *op2, you store in formula in db or xml, because java new script engine allows you to define your js function in java, you can just simply replace op1 and op2 at run time, and send the defined function to js engine. this way you just take advantage of exsiting js engine parser and interpreter. You do not
B*****g 发帖数: 34098
34
this one I decide. I want to do it in java
then
【在 F****n 的大作中提到】 : You must first know what the expression language is. If you don't know, then : there's no solution. : : get
B*****g 发帖数: 34098
35
Solution storing data in columns (no matter is physical or logical) has been turned down by my manager. Solution use pl/sql as script language for all operations is also turned down. That is why I ask here. My manager asked " why can not you do it in java?" I am new to java, his is pre^10-new
real a name used
【在 s******e 的大作中提到】 : if so, even dynamic functions are not enough. Dynamic functions are not real : dynamic, you still need to code them in your code base. : what you need is either using db or xml file or any format file to act as a : configuration file, treating your first name as operand one, and last name : as operand two (if you are sure that you will only have two operands, and : they will be stored in columns that you know ahead. Otherwise if even the : operands are unknown at compilation time, it will be way too compli
c*****t 发帖数: 1879
36
你没这方面的知识。没戏。
【在 B*****g 的大作中提到】 : this one I decide. I want to do it in java : : then
【在 B*****g 的大作中提到】 : Solution storing data in columns (no matter is physical or logical) has been : turned down by my manager. : Solution use pl/sql as script language for all operations is also turned : down. : That is why I ask here. : My manager asked " why can not you do it in java?" : I am new to java, his is pre^10-new : : real : a
Use script with customized context. People do that kind of things all the time. You can either use Rhino (then the expression is officially javascript , not java), or use BeanShell.
f + l is just an example. Real world can be complicate. Like first remove special characters from f and l, then trim them, then get first 20 characters, then trim again, then uppercase. More complicate example may involve if/else
You must first know what the expression language is. If you don't know, then there's no solution.
get
【在 B*****g 的大作中提到】 : f + l is just an example. : Real world can be complicate. : Like first remove special characters from f and l, then trim them, then get : first 20 characters, then trim again, then uppercase. : More complicate example may involve if/else
s*e
33 楼
if so, even dynamic functions are not enough. Dynamic functions are not real dynamic, you still need to code them in your code base. what you need is either using db or xml file or any format file to act as a configuration file, treating your first name as operand one, and last name as operand two (if you are sure that you will only have two operands, and they will be stored in columns that you know ahead. Otherwise if even the operands are unknown at compilation time, it will be way too compli
s*e
34 楼
just have thought, you may be able to take advantage of jdk 1.6 with mozilla rhino(the only built-in Jscript implemntation support in hotspot) for example you have a formula (op1 * 13 - op2)/13 *op2, you store in formula in db or xml, because java new script engine allows you to define your js function in java, you can just simply replace op1 and op2 at run time, and send the defined function to js engine. this way you just take advantage of exsiting js engine parser and interpreter. You do not
B*g
35 楼
this one I decide. I want to do it in java
then
【在 F****n 的大作中提到】 : You must first know what the expression language is. If you don't know, then : there's no solution. : : get
B*g
36 楼
Solution storing data in columns (no matter is physical or logical) has been turned down by my manager. Solution use pl/sql as script language for all operations is also turned down. That is why I ask here. My manager asked " why can not you do it in java?" I am new to java, his is pre^10-new
real a name used
【在 s******e 的大作中提到】 : if so, even dynamic functions are not enough. Dynamic functions are not real : dynamic, you still need to code them in your code base. : what you need is either using db or xml file or any format file to act as a : configuration file, treating your first name as operand one, and last name : as operand two (if you are sure that you will only have two operands, and : they will be stored in columns that you know ahead. Otherwise if even the : operands are unknown at compilation time, it will be way too compli
c*t
37 楼
你没这方面的知识。没戏。
【在 B*****g 的大作中提到】 : this one I decide. I want to do it in java : : then
【在 B*****g 的大作中提到】 : Solution storing data in columns (no matter is physical or logical) has been : turned down by my manager. : Solution use pl/sql as script language for all operations is also turned : down. : That is why I ask here. : My manager asked " why can not you do it in java?" : I am new to java, his is pre^10-new : : real : a
Use script with customized context. People do that kind of things all the time. You can either use Rhino (then the expression is officially javascript , not java), or use BeanShell.
