亲宝软件园·资讯

展开

Java jOOR

​ 你呀不牛   ​ 人气:0

前言

Java中的原生反射库虽然方法不多,但写起来却非常繁琐, 比如:

public static <T> T create(HttpRequest httpRequest) {
    Object httpRequestEntity = null;
    try {
        Class<T> httpRequestEntityCls = (Class<T>) Class.forName(HttpProcessor.PACKAGE_NAME + "." + HttpProcessor.CLASS_NAME);
        Constructor con = httpRequestEntityCls.getConstructor(HttpRequest.class);
        httpRequestEntity = con.newInstance(httpRequest);
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (InstantiationException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    }
    return (T) httpRequestEntity;
}

就实现一个对象的构造都需要写一长串代码,特别是异常处理非常污染视觉

发现有一个第三方库:jOOR,通过链式DSL接口,简化了反射过程,

比如:

@Test
void should_get_World() {
    String result = Reflect.onClass("java.lang.String") // 类似Class.forName()
        .create("Hello World")     // 调用构造器
        .call("substring", 6)      // 调用方法
        .call("toString")          // 调用方法
        .get();                    // 获取最终包装类

    assertThat(result).isEqualTo("World");
}

再比如:原有java代码写法:

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);
}

采用jOOR后的写法:

Employee[] employees = on(department).call("getEmployees").get();
 
for (Employee employee : employees) {
  Street street = on(employee).call("getAddress").call("getStreet").get();
  System.out.println(street);
}

已经非常的简洁了。

jOOR特点

常用API测试

测试类:

class Person {
    private String name;
    private int age;

    public Person() {
    }
    public Person(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Person{" +
            "name='" + name + '\'' +
            ", age=" + age +
            '}';
    }
}

测试APIS

@Test
void test_joor_apis() {
    // 【创建类】
    Person person = Reflect.onClass(Person.class).create("steven").get();// 有参构造器
    //Person person = Reflect.onClass(Person.class).create().get(); // 无参构造器
    assertThat(person.toString()).isEqualTo("Person{name='steven', age=0}");

    // 【调用方法】
    Reflect.on(person).call("setName", "steven2");
    String name = Reflect.on(person).call("getName").toString();
    assertThat(name).isEqualTo("steven2");

    // 【设置变量的值】
    int age = Reflect.on(person).set("age", 18).get("age");
    assertThat(age).isEqualTo(18);

    // 【得到变量】
    name = Reflect.on(person).field("name").get();// 方式一
    assertThat(name).isEqualTo("steven2");
    name = Reflect.on(person).get("name");// 方式二
    assertThat(name).isEqualTo("steven2");
}

代理功能

jOOR代理是实现的静态代理功能,首先创建静态代理相关类

interface HelloWorld {
    void print();
}
class HelloWorldImpl implements HelloWorld {
    public void print() {
        System.out.println("Hello World");
    }
}
class StaticProxy implements HelloWorld {
    private HelloWorld helloWorld;

    public StaticProxy(HelloWorld helloWorld) {
        this.helloWorld = helloWorld;
    }
    public void print() {
        System.out.println("Before Hello World!");
        helloWorld.print();
        System.out.println("After Hello World!");
    }
}

使用方法区别:

传统方式:

@Test
void test_proxy_normal() {
    StaticProxy staticProxy = new StaticProxy(new HelloWorldImpl());

    staticProxy.print();
}

jOOR实现方式

@Test
void test_proxy_jOOR() {
    Reflect.onClass(StaticProxy.class)//反射调用StaticProxy
            .create(new HelloWorldImpl())//调用构造器
            .as(HelloWorld.class)//作为HelloWorld接口的代理
            .print();
}

此时要求代理类和业务类具有相同的方法,才能通过调用代理的方法,负责抛出ReflectException异常

org.joor.ReflectException: java.lang.NoSuchMethodException: No similar method print with params [] could be found on type class StaticProxy.

	at org.joor.Reflect.call(Reflect.java:585)
	at org.joor.Reflect$1.invoke(Reflect.java:756)

特殊情况

当业务类为map类型,此时会把POJO的getter和setter转换成map的put和get

 // [#14] Emulate POJO behaviour on wrapped map objects
catch (ReflectException e) {
    if (isMap) {
        Map<String, Object> map = (Map<String, Object>) object;
        int length = (args == null ? 0 : args.length);

        if (length == 0 && name.startsWith("get")) {
            return map.get(property(name.substring(3)));
        }
        else if (length == 0 && name.startsWith("is")) {
            return map.get(property(name.substring(2)));
        }
        else if (length == 1 && name.startsWith("set")) {
            map.put(property(name.substring(3)), args[0]);
            return null;
        }
    }

动态编译

jOOR提供了可选的依赖java.compiler 可以简化 javax.tools.JavaCompiler 编译代码,

如下所示:

@Test
void test_compile_on_runtime() {
    Supplier<String> supplier = Reflect.compile(
        "com.example.HelloWorld",
        "package com.example;\n" +
        "class HelloWorld implements java.util.function.Supplier<String> {\n" +
        "    public String get() {\n" +
        "        return \"Hello World!\";\n" +
        "    }\n" +
        "}\n").create().get();


    String result = supplier.get();

    assertThat(result).isEqualTo("Hello World!");
}

结论

通过以上案例可以看出,jOOR由于其链式编程的特性,对代码的简化和可扩展性要强Java自带反射库和其他第三方库(apache、hutool等),且其包含了一些高级应用,如代理等。

加载全部内容

相关教程
猜你喜欢
用户评论