Python桥接Java工具JPype

以你之姓@ 2022-06-17 14:36 159阅读 0赞

JPype这玩意可以桥接Java,在Python中调用Java的类，比较好用，对外接口不多，不过需要注意的是python和java类型匹配的问题.可以参考官方文档

http://jpype.sourceforge.net/doc/user-guide/userguide.html

过程中遇到个小问题，设置classpath时，-D前面留了一个空格，导致始终找不到类的错误，很坑爹。

jvmArg = "-Djava.class.path=%s" % ext\_classpath  
jpype.startJVM(jvmpath,jvmArg)

JPype defines different leels of "match" between Python objects and Java types. These levels are :

*  **none**, There is no way to convert.
 *  **explicit (E)**, JPype canconvert ot the desired type, but only explicitly via the wrapper classes. This means the proper wrapper class will access this type as argument.
 *  **implicit (I)**, JPype will convert as needed.
 *  **exact> (X)**, Like implicit, but when deciding with method overload to use, one wj=here all the paramters match "exact" will take precedence over "implicit" matches.

<table> 
 <tbody> 
  <tr> 
   <th>&nbsp;</th> 
   <th> 
    <div>
      byte 
    </div> </th> 
   <th> 
    <div>
      short 
    </div> </th> 
   <th> 
    <div>
      int 
    </div> </th> 
   <th> 
    <div>
      long 
    </div> </th> 
   <th> 
    <div>
      float 
    </div> </th> 
   <th> 
    <div>
      double 
    </div> </th> 
   <th> 
    <div>
      boolean 
    </div> </th> 
   <th> 
    <div>
      char 
    </div> </th> 
   <th> 
    <div>
      String 
    </div> </th> 
   <th> 
    <div>
      Array 
    </div> </th> 
   <th> 
    <div>
      Object 
    </div> </th> 
   <th> 
    <div>
      Class 
    </div> </th> 
  </tr> 
  <tr> 
   <th>int</th> 
   <td> 
    <div>
      I (1) 
    </div> </td> 
   <td> 
    <div>
      I (1) 
    </div> </td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td> 
    <div>
      I 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      X (10) 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>long</th> 
   <td> 
    <div>
      I (1) 
    </div> </td> 
   <td> 
    <div>
      I (1) 
    </div> </td> 
   <td> 
    <div>
      I (1) 
    </div> </td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>float</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      I (1) 
    </div> </td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>sequence</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>dictionary</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>string</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      I (2) 
    </div> </td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>unicode</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      I (2) 
    </div> </td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JByte</th> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JShort</th> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JInt</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JLong</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JFloat</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JDouble</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JBoolean</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JString</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      I (3) 
    </div> </td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JChar</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      X 
    </div> </td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JArray</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      I/X (4) 
    </div> </td> 
   <td> 
    <div>
      I (5) 
    </div> </td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JObject</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      I/X (6) 
    </div> </td> 
   <td> 
    <div>
      I/X (7) 
    </div> </td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JavaObject</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      I (8) 
    </div> </td> 
   <td>&nbsp;</td> 
  </tr> 
  <tr> 
   <th>JavaClass</th> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td>&nbsp;</td> 
   <td> 
    <div>
      I (9) 
    </div> </td> 
   <td> 
    <div>
      X 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

(1) Conversion will occur if the Python value fits in the java native type.

(2) Conversion occurs if the python string or unicode is of length 1

(3) The required object must be of a type compatible with **java.lang.String** (**java.lang.Object**, **java.util.Comparable**)

(4) Number of dimensions must match, and the types must be compatible

(5) Only when the required type is **java.lang.Object**

(6) Only if the JObject wrapper's specified type is an compatible array class.

(7) Only if the required type is compatible with the wrappers's specified type. The actual type of the java object is not considered.

(8) Only if the requireds type is compatible with the Java Object actual type.

(9) Only when the required type is **java.lang.Object** or  **java.lang.Class**

(10) only the values True and False are implitly converted to booleans.

### Converting from java to python ###

The rules here are much simpler.