apt处理自定义annotation

程序员文章站 2022-04-05 22:25:47

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package annotations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface ExtractInterface {
	String value();
}

package annotations;

//包含待解析annotation的类
@ExtractInterface("IMultiplier")
public class Multiplier {
	public int multiply(int x, int y) {
		int total = 0;
		for (int i = 0; i < x; i++)
			total = add(total, y);
		return total;
	}

	private int add(int x, int y) {
		return x + y;
	}
}

package annotations;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import com.sun.mirror.apt.AnnotationProcessor;
import com.sun.mirror.apt.AnnotationProcessorEnvironment;
import com.sun.mirror.declaration.MethodDeclaration;
import com.sun.mirror.declaration.Modifier;
import com.sun.mirror.declaration.ParameterDeclaration;
import com.sun.mirror.declaration.TypeDeclaration;

//annotation处理类
public class InterfaceExtractorProcessor implements AnnotationProcessor {
	private final AnnotationProcessorEnvironment env;
	private List<MethodDeclaration> methods = new ArrayList<MethodDeclaration>();

	public InterfaceExtractorProcessor(AnnotationProcessorEnvironment env) {
		this.env = env;
	}

	@Override
	public void process() {
		for (TypeDeclaration type : env.getSpecifiedTypeDeclarations()) {
			ExtractInterface intf = type.getAnnotation(ExtractInterface.class);
			if (intf == null)
				continue;

			for (MethodDeclaration method : type.getMethods())
				if (method.getModifiers().contains(Modifier.PUBLIC)
						&& !method.getModifiers().contains(Modifier.STATIC))
					methods.add(method);

			if (methods.size() > 0) {

				PrintWriter writer = null;
				try {
					writer = env.getFiler().createSourceFile(intf.value());
					writer.println("package "
							+ type.getPackage().getQualifiedName() + ";");
					writer.println();
					writer.println("public interface " + intf.value() + " {");

					for (MethodDeclaration method : methods) {
						writer.print("\tpublic " + method.getReturnType() + " "
								+ method.getSimpleName() + "(");

						Collection<ParameterDeclaration> params = method
								.getParameters();
						int i = 0;
						int len = params.size();
						for (ParameterDeclaration param : params) {
							writer.print(param.getType() + " "
									+ param.getSimpleName());
							if (++i < len)
								writer.print(", ");
						}
						writer.println(");");
					}
					writer.println("}");
				} catch (IOException e) {
					throw new RuntimeException(e);
				} finally {
					if (writer != null) {
						try {
							writer.close();
						} catch (Throwable ex) {
						}
					}
				}
			}
		}
	}
}

package annotations;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Set;

import com.sun.mirror.apt.AnnotationProcessor;
import com.sun.mirror.apt.AnnotationProcessorEnvironment;
import com.sun.mirror.apt.AnnotationProcessorFactory;
import com.sun.mirror.declaration.AnnotationTypeDeclaration;

//每个annotation处理器类 需要有一个工厂类去创建它
public class InterfaceExtractorProcessorFactory implements
		AnnotationProcessorFactory {
	@Override
	public AnnotationProcessor getProcessorFor(
			Set<AnnotationTypeDeclaration> set,
			AnnotationProcessorEnvironment env) {
		return new InterfaceExtractorProcessor(env);
	}

	@Override
	public Collection<String> supportedAnnotationTypes() {
		return Collections.unmodifiableCollection(Arrays
				.asList("annotations.ExtractInterface"));
	}

	@Override
	public Collection<String> supportedOptions() {
		return Collections.emptySet();
	}
}

编译ExtractInterface.java
InterfaceExtractorProcessor.java
InterfaceExtractorProcessorFactory.java

最后执行
apt -factory annotations.InterfaceExtractorProcessorFactory annotations/Multiplier.java -s . //-s 表明将生成的源文件存放在哪里

--------------------------------------------------
将访问者模式应用到annotation处理上

package annotations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface DBTable {
	String value();
}

package annotations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Constraints {
	boolean primaryKey() default false;

	boolean allowNull() default true;

	boolean unique() default false;
}

package annotations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface SQLString {
	int value();

	String name() default "";

	Constraints constraints() default @Constraints;
}

package annotations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface SQLInteger {
	String name() default "";

	Constraints constraints() default @Constraints;
}

package annotations;

@DBTable("t_member")
public class Member {
	@SQLInteger(constraints = @Constraints(primaryKey = true))
	private int id;
	@SQLString(value = 50, constraints = @Constraints(allowNull = false))
	private String firstname;
	@SQLString(50)
	private String lastname;
	@SQLInteger
	private int age;
	@SQLString(name = "addr", value = 255)
	private String address;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getFirstname() {
		return firstname;
	}

	public void setFirstname(String firstname) {
		this.firstname = firstname;
	}

	public String getLastname() {
		return lastname;
	}

	public void setLastname(String lastname) {
		this.lastname = lastname;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}
}

package annotations;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Set;

import com.sun.mirror.apt.AnnotationProcessor;
import com.sun.mirror.apt.AnnotationProcessorEnvironment;
import com.sun.mirror.apt.AnnotationProcessorFactory;
import com.sun.mirror.declaration.AnnotationTypeDeclaration;
import com.sun.mirror.declaration.ClassDeclaration;
import com.sun.mirror.declaration.FieldDeclaration;
import com.sun.mirror.declaration.TypeDeclaration;
import com.sun.mirror.util.DeclarationVisitors;
import com.sun.mirror.util.SimpleDeclarationVisitor;

public class TableCreationProcessorFactory implements
		AnnotationProcessorFactory {

	@Override
	public AnnotationProcessor getProcessorFor(
			Set<AnnotationTypeDeclaration> set,
			AnnotationProcessorEnvironment env) {
		return new TableCreationProcessor(env);
	}

	@Override
	public Collection<String> supportedAnnotationTypes() {
		return Collections.unmodifiableCollection(Arrays.asList(
				"annotations.DBTable", "annotations.Constraints",
				"annotations.SQLString", "annotations.SQLInteger"));
	}

	@Override
	public Collection<String> supportedOptions() {
		return Collections.emptySet();
	}

	private static class TableCreationProcessor implements AnnotationProcessor {
		private final AnnotationProcessorEnvironment env;
		private String sql = "";
		private static String LINE_SEPARATOR = System
				.getProperty("line.separator");

		public TableCreationProcessor(AnnotationProcessorEnvironment env) {
			this.env = env;
		}

		@Override
		public void process() {
			for (TypeDeclaration type : env.getSpecifiedTypeDeclarations()) {
				type.accept(DeclarationVisitors.getDeclarationScanner(
						new TableCreationVisitor(), DeclarationVisitors.NO_OP));
				sql = sql.substring(0, sql.length() - LINE_SEPARATOR.length()
						- 1);
				sql += LINE_SEPARATOR + ")";
				System.out.println("The creation sql is:\n" + sql);
				sql = "";
			}
		}

		private class TableCreationVisitor extends SimpleDeclarationVisitor {
			@Override
			public void visitClassDeclaration(ClassDeclaration classdeclaration) {
				DBTable dbTable = classdeclaration.getAnnotation(DBTable.class);
				if (dbTable != null) {
					sql += "CREATE TABLE ";
					sql += (dbTable.value().length() < 1) ? classdeclaration
							.getSimpleName().toUpperCase() : dbTable.value();
					sql += "(" + LINE_SEPARATOR;
				}
			}

			@Override
			public void visitFieldDeclaration(FieldDeclaration fielddeclaration) {
				String columnName = "";
				if (fielddeclaration.getAnnotation(SQLString.class) != null) {
					SQLString sString = fielddeclaration
							.getAnnotation(SQLString.class);
					if (sString.name().length() < 1)
						columnName = fielddeclaration.getSimpleName()
								.toUpperCase();
					else
						columnName = sString.name();
					sql += "\t" + columnName + " VARCHAR(" + sString.value()
							+ ")" + getConstraints(sString.constraints()) + ","
							+ LINE_SEPARATOR;
				}

				if (fielddeclaration.getAnnotation(SQLInteger.class) != null) {
					SQLInteger sInteger = fielddeclaration
							.getAnnotation(SQLInteger.class);
					if (sInteger.name().length() < 1)
						columnName = fielddeclaration.getSimpleName()
								.toUpperCase();
					else
						columnName = sInteger.name();
					sql += "\t" + columnName + " INT"
							+ getConstraints(sInteger.constraints()) + ","
							+ LINE_SEPARATOR;
				}
			}

			private String getConstraints(Constraints constraints) {
				String result = "";
				if (!constraints.allowNull())
					result += " NOT NULL";
				if (constraints.primaryKey())
					result += " PRIMARY KEY";
				if (constraints.unique())
					result += " UNIQUE";
				return result;
			}

		}
	}

}

结果

apt处理自定义annotation

博客分类： java aptannotation

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