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