java 反射机制

package reflection;@AnnotationUserTable("datebaseExample")public class User {  @AnnotationUserField(uName="name",type="varchar",length=10)  private String name;  @AnnotationUserField(uName="age",type="int",length=3)  private int age;  @AnnotationUserField(uName="sex",type="char",length=2)  private String sex;  public User() {    super();  }  public User(String name, int age, String sex) {    super();    this.name = name;    this.age = age;    this.sex = sex;  }  public String getName() {    return name;  }  public void setName() {    this.name = "test";  }  public int getAge() {    return age;  }  public String getSex() {    return sex;  }  public void setSex(String sex) {    this.sex = sex;  }}bean:User

package reflection;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;@Target(value={ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME) public @interface AnnotationUserTable {  String value();}自定义注解：类注解

package reflection;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;@Target(value={ElementType.FIELD})@Retention(RetentionPolicy.RUNTIME)public @interface AnnotationUserField {  String uName();  String type();  int length();  }自定义注解：属性注解

package reflection;import java.lang.reflect.Constructor;import java.lang.reflect.Field;import java.lang.reflect.Method;public class Demo01 {  static Class<?> c = null;  public static void main(String[] args) {      try {        c = Class.forName("reflection.User");      } catch (ClassNotFoundException e) {        e.printStackTrace();      }    test();//获取类的属性、方法等信息  }  static void test(){    try {      // 获取类的名称      System.out.println("获取类的名称");      System.out.println("getName():" + c.getName());// 获得包名+类名      System.out.println("getSimpleName():" + c.getSimpleName());// 获得类名      System.out.println("getCanonicalName():" + c.getCanonicalName());// 获得类名      System.out.println("*******************************");      // 获取属性信息      System.out.println("获取属性信息");      Field[] fields = c.getDeclaredFields();      // Field[] fields = c.getFields(); 只能获取public修饰的属性信息      for (Field f : fields) {        String fName = f.getName();        System.out.println(c.getDeclaredField(fName));      }      System.out.println("*******************************");      // 获取方法信息      System.out.println("获取方法信息");      Method[] methods = c.getDeclaredMethods();      for (Method m : methods) {        // String mName = m.getName();        System.out.println(m.getName() + "-->" + m);      }      System.out.println("通过名称单独获取对应的getName方法:" + c.getDeclaredMethod("getName"));      System.out.println("通过名称单独获取对应的setSex方法:" + c.getDeclaredMethod("setSex", String.class));// 方法有参，必须传递参数类型      System.out.println("*******************************");      // 获取构造器信息      System.out.println("获取构造器信息");      Constructor<?>[] constructor = c.getConstructors();      for (Constructor<?> cons : constructor) {        System.out.println(cons);      }    } catch (NoSuchFieldException | SecurityException e) {      e.printStackTrace();    } catch (NoSuchMethodException e) {      e.printStackTrace();    }  }}main1：通过反射机制获取类的基本信息

获取类的名称getName():reflection.UsergetSimpleName():UsergetCanonicalName():reflection.User*******************************获取属性信息private java.lang.String reflection.User.nameprivate int reflection.User.ageprivate java.lang.String reflection.User.sex*******************************获取方法信息getName-->public java.lang.String reflection.User.getName()setName-->public void reflection.User.setName()setSex-->public void reflection.User.setSex(java.lang.String)getSex-->public java.lang.String reflection.User.getSex()getAge-->public int reflection.User.getAge()通过名称单独获取对应的getName方法:public java.lang.String reflection.User.getName()通过名称单独获取对应的setSex方法:public void reflection.User.setSex(java.lang.String)*******************************获取构造器信息public reflection.User()public reflection.User(java.lang.String,int,java.lang.String)View Console

package reflection;import java.lang.reflect.Field;/** * 获取类的属性、方法等信息 * 1.获取元素对象（如属性）（注意：读取类的注解，看似要少一步） * 2.获取该元素对象的指定类型的注解对象 * 3.读取注解对象相应的值 */public class Test02 {  static Class<?> c = null;  public static void main(String[] args) {      try {        c = Class.forName("reflection.User");      } catch (ClassNotFoundException e) {        e.printStackTrace();      }    test();  }  static void test(){    try {      // 获取类的指定注解      System.out.println("***********类的指定注解**************");      AnnotationUserTable table = (AnnotationUserTable)c.getAnnotation(AnnotationUserTable.class);      System.out.println(table.value());      // 获取属性的指定注解      System.out.println("***********属性的指定注解*************");      Field field = c.getDeclaredField("name");      AnnotationUserField annoField = (AnnotationUserField)field.getAnnotation(AnnotationUserField.class);      System.out.println(annoField.uName()+"/t"+annoField.type()+"/t"+annoField.length());      // 根据获得的表名、字段的信息，拼写出DDL语句，然后通过JDBC连接数据库查询    } catch (NoSuchFieldException e) {      e.printStackTrace();    } catch (SecurityException e) {      e.printStackTrace();    }  }}

***********类的指定注解**************datebaseExample***********属性的指定注解*************name  varchar  10

package reflection;import java.lang.reflect.Method;import java.lang.reflect.Type;import java.util.List;import java.util.Map;/** * 通过反射机制获取泛型 * @author Administrator * */public class Test03 {    public static void main(String[] args) {    Class<?> c = Test03.class;    try {      System.out.println("*******获取参数值的类型**********");      Method m1 = c.getDeclaredMethod("method01", Map.class,List.class);      Type[] types = m1.getGenericParameterTypes();      for(Type t:types){        System.out.println(t.getTypeName());        System.out.println(t.toString());              }      System.out.println("*******获取返回值的类型**********");      Method m2 = c.getDeclaredMethod("method02");      Type ret = m2.getGenericReturnType();      System.out.println(ret.getTypeName());      System.out.println(ret.toString());    } catch (NoSuchMethodException | SecurityException e) {      e.printStackTrace();    }  }  public void method01(Map<String,String> args1,List<Integer> args2){  }  public Map<String,String> method02(){    return null;  }}通过反射机制获取泛型信息

java.util.Map<java.lang.String, java.lang.String>java.util.Map<java.lang.String, java.lang.String>java.util.Map<java.lang.String, java.lang.String>java.util.Map<java.lang.String, java.lang.String>java.util.List<java.lang.Integer>java.util.List<java.lang.Integer>View Console