是否有用于处理java中反射的开源实用程序或jar?
我正在动态地将方法传递给类,我想获取返回值。
例如:
class Department {
String name ;
Employee[] employees;
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public Employee[] getEmployes() {
return employees;
}
}
我想将所有员工打印到控制台输出,而是在运行时将其打印出来,如下所示:
Department dept = new Department();
// add employees..
getEmployeeNames(dept,"getEmployees.getAddress.getStreet");
// So the user says they want employee street, but we don't know that
// until run-tme.
是否有反思的开源来容纳这样的东西?
答案 0 :(得分:20)
除了使用Apache BeanUtils或直接使用java.lang.reflect
API,正如其他人所建议的那样,你也可以使用我创建的jOOR来减少在Java中使用反射的冗长程度。您的示例可以像这样实现:
Employee[] employees = on(department).call("getEmployees").get();
for (Employee employee : employees) {
Street street = on(employee).call("getAddress").call("getStreet").get();
System.out.println(street);
}
与Java中的正常反射相同的示例:
try {
Method m1 = department.getClass().getMethod("getEmployees");
Employee employees = (Employee[]) m1.invoke(department);
for (Employee employee : employees) {
Method m2 = employee.getClass().getMethod("getAddress");
Address address = (Address) m2.invoke(employee);
Method m3 = address.getClass().getMethod("getStreet");
Street street = (Street) m3.invoke(address);
System.out.println(street);
}
}
// There are many checked exceptions that you are likely to ignore anyway
catch (Exception ignore) {
// ... or maybe just wrap in your preferred runtime exception:
throw new RuntimeException(e);
}
此外,jOOR以更方便的方式包装java.lang.reflect.Proxy
功能:
interface StringProxy {
String mySubString(int beginIndex);
}
// You can easily create a proxy of a custom type to a jOOR-wrapped object
String substring = on("java.lang.String")
.create("Hello World")
.as(StringProxy.class)
.mySubString(6);
答案 1 :(得分:5)
当我看到它时,这种东西总会敲响警钟。
话虽这么说,我通常认为JXPath(http://commons.apache.org/jxpath/users-guide.html)对于这类问题是最合理的解决方案,如果它不能以更加工程化的方式解决:
import org.apache.commons.jxpath.JXPathContext;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
/**
*/
public class JXPather {
public static void main(String[] args) {
Department d = new Department();
d.employees.add(new Employee(new Address("wherever a")));
d.employees.add(new Employee(new Address("wherever b")));
d.employees.add(new Employee(new Address("wherever c")));
d.employees.add(new Employee(new Address("wherever def")));
JXPathContext context = JXPathContext.newContext(d);
// access matched xpath objects by iterating over them
for (Iterator iterator = context.iterate("/employees/address/street"); iterator.hasNext();) {
System.out.println(iterator.next());
}
// or directly via standard xpath expressions
System.out.println("street of third employee is: "+context.getValue("/employees[3]/address/street"));
// supports most (or all ?) xpath expressions
for (Iterator iterator = context.iterate("/employees/address/street[string-length(.) > 11]"); iterator.hasNext();) {
System.out.println("street length longer than 11 c'ars:"+iterator.next());
}
}
static public class Department {
List<Employee> employees = new ArrayList<Employee>();
public List<Employee> getEmployees() {
return employees;
}
}
static public class Employee {
Address address;
Employee(Address address) {
this.address = address;
}
public Address getAddress() {
return address;
}
}
static public class Address {
String street;
Address(String street) {
this.street = street;
}
public String getStreet() {
return street;
}
}
}
答案 2 :(得分:1)
您可以使用apache beanutils:http://commons.apache.org/beanutils/
答案 3 :(得分:1)
您可以像其他人建议的那样使用某些第三方库,或者可以自己手动完成这个技巧,但这并不难。以下示例应说明可以采取的方式:
class Department {
Integer[] employees;
public void setEmployes(Integer[] employees) { this.employees = employees; }
public Integer[] getEmployees() { return employees; }
}
Department dept = new Department();
dept.setEmployes(new Integer[] {1, 2, 3});
Method mEmploees = Department.class.getMethod("getEmployees", new Class[] {});
Object o = mEmploees.invoke(dept, new Object[] {});
Integer[] employees = (Integer[])o;
System.out.println(employees[0].doubleValue());;