swift是一个用于创建thrift 序列化类型和服务的java工具库，使用swfit可以生成非常简洁的java代码。并且更重要的是可以通过java代码生成接口描述文件(Thrift interface description language,IDL).
多数情况下，服务端的应用都是java写的。使用swift提供的工具，可以直接生成IDL，再用IDL生成其他语言的client端代码 (java,cpp,python…)

下面的TestService.java定义了一个简单的服务接口，本文以实例的例子说明将这个服务接口生成thrift client端代码的过程：
TestService.java

package net.gdface.facelog;
import com.facebook.swift.service.ThriftMethod;
import com.facebook.swift.service.ThriftService;
@ThriftService
public interface TestService {
    @ThriftMethod
    public void setBean(TestBean bean);
    @ThriftMethod
    public TestBean getBean() throws ServiceRuntime;
}

TestBean.java

package net.gdface.facelog;
import com.facebook.swift.codec.ThriftField;
import com.facebook.swift.codec.ThriftStruct;

@ThriftStruct
public final class TestBean{
    private Integer id;
    public TestBean() {
    }
    @ThriftField(1)
    public Integer getId() {
        return id;
    }
    @ThriftField()
    public void setId(Integer id) {
        this.id = id;
    }
}

下载Swift2Thrift Code Generator

我们首先要从TestService.java生成 IDL文件。这需要用到swift提供的工具：Swift2Thrift Code Generator
为了便于在命令行执行，要下载包含所有依赖库的standalone版本

URL地址下载

maven仓库 0.14.2 standalone版本下载地址 ：
http://central.maven.org/maven2/com/facebook/swift/swift2thrift-generator-cli/0.14.2/swift2thrift-generator-cli-0.14.2-standalone.jar

maven命令下载

执行maven命令下载swift2thrift-generator-cli-0.14.2-standalone.jar到lib文件夹下
(‘^’是windows shell下的分行符,linux shell下请将 ‘^’ 换成 ‘\’)

mvn org.apache.maven.plugins:maven-dependency-plugin:2.8:get ^
  -DremoteRepositories=central::default::http://repo1.maven.apache.org/maven2 ^
  -Dartifact=com.facebook.swift:swift2thrift-generator-cli:0.14.2:jar:standalone ^
  -Ddest=lib/swift2thrift-generator-cli-0.14.2-standalone.jar

这里-Dartifact参数中的 0.14.2是指定swift的版本号,如果换成RELEASE,则下载当前最高版本。
但是swift 0.14.2以后的版本都是java1.8编译的。而我用的java是1.7，所以这里必须指定版本号。
-Ddest指定保存jar包的路径，如果不指定，则下载到maven本地仓库中。
-DremoteRepositories 指定远程仓库，可省略此参数

[INFO] Scanning for projects…
[INFO]
[INFO] ————————————————————————
[INFO] Building facelog-main 1.0-SNAPSHOT
[INFO] ————————————————————————
[INFO]
[INFO] — maven-dependency-plugin:2.8:get (default-cli) @ facelog-main —
[INFO] Resolving com.facebook.swift:swift2thrift-generator-cli:jar:standalone:0.
14.2 with transitive dependencies
Downloading: http://maven.aliyun.com/nexus/content/groups/public/com/facebook/sw
ift/swift2thrift-generator-cli/0.14.2/swift2thrift-generator-cli-0.14.2.pom
Downloaded: http://maven.aliyun.com/nexus/content/groups/public/com/facebook/swi
ft/swift2thrift-generator-cli/0.14.2/swift2thrift-generator-cli-0.14.2.pom (2.8
kB at 5.3 kB/s)
Downloading: http://maven.aliyun.com/nexus/content/groups/public/com/facebook/sw
ift/swift2thrift-generator-cli/0.14.2/swift2thrift-generator-cli-0.14.2-standalo
ne.jar
Downloaded: http://maven.aliyun.com/nexus/content/groups/public/com/facebook/swi
ft/swift2thrift-generator-cli/0.14.2/swift2thrift-generator-cli-0.14.2-standalon
e.jar (11 MB at 616 kB/s)
[WARNING] destination/dest parameter is deprecated: it will disappear in future
version.
[INFO] copying J:\maven_repository\com\facebook\swift\swift2thrift-generator-cli
\0.14.2\swift2thrift-generator-cli-0.14.2-standalone.jar to J:\facelog\facelog-m
ain\lib\swift2thrift-generator-cli-0.14.2-standalone.jar
[WARNING] Notice transitive dependencies won’t be copied.
[INFO] ————————————————————————
[INFO] BUILD SUCCESS
[INFO] ————————————————————————
[INFO] Total time: 20.526 s
[INFO] Finished at: 2017-10-11T15:58:03+08:00
[INFO] Final Memory: 15M/436M
[INFO] ————————————————————————

生成 IDL文件

命令行执行如下命令生成IDL文件 TestService.thrift

java -cp lib\swift2thrift-generator-cli-0.14.2-standalone.jar;target\test-classes ^
    com.facebook.swift.generator.swift2thrift.Main ^
    -package net.gdface.facelog ^
    TestService  ^
    -namespace py gdface.thrift -namespace java com.gdface -namespace cpp gdface ^
    -out TestService.thrift ^
    -recursive

生成的TestService.thrift，文件中不仅有TestService的定义还有涉及的类型TestBean的定义：

namespace java.swift net.gdface.facelog
namespace py gdface.thrift
namespace java com.gdface
namespace cpp gdface
struct TestBean {
  1:  i32 id;
}

service TestService {
  TestBean getBean();
  void setBean(1:  TestBean arg0);
}

关于Swift2Thrift Code Generator的大部分的命令行参数说明参见Swift2Thrift Code Generator
但是 -recursive 这个参数，官方网站并没有说明，只有执行java -jar lib\swift2thrift-generator-cli-0.14.2-standalone.jar时才会显示：

J:\facelog\facelog-main>java -jar lib\swift2thrift-generator-cli-0.14.2-standalo
ne.jar
Usage: Swift2ThriftGenerator [options] <swift-class-name...>
  Options:
    -allow_multiple_packages
       Allow input classes to reside in different packages. The value of this
       flag defines the generated java.swift namespace. Note that Swift classes
       generated from the resultant Thrift file will all reside in one Java pack
age
    -package,-default_package
       Default package for unqualified classes
       Default: <empty string>
    -map
       Map of external type or service to include file
    -namespace
       Namespace for a particular language to include
    -out
       Thrift IDL output file,defaults to stdout
    -recursive
       Generate all types transitively reachable from the specified types and
       services       
       Default: false
    -v,-verbose
       Show verbose messages
       Default: false

-recursive是指定递归生成所有service接口中涉及的数据类型的IDL定义。这个参数很重要。
比如本例中TestService.java中还涉及到TestBean.java类，如果没有这个参数，还需要单独为TestBean.java再执行一次Swift2ThriftGenerator生成 IDL，并且要在生成TestService.java的IDL时还要用-map告诉程序TestBean的IDL文件的位置，如果service接口中有多个自定的类型的时候，代码维护就非常麻烦。
有了这个参数，只要对service接口类型执行一次Swift2ThriftGenerator就可以生成完整的IDL定义文件。

下载Swift Code Generator Tool

有了前面生成的IDL文件( TestService.thrift)。就可以用swift提供的另一个工具：Swift Code Generator Tool来生成Client代码了.

Swift Code Generator Tool的下载方式与Swift2Thrift Code Generator差不多：

url下载

maven仓库 0.14.2 standalone版本下载地址 ：
http://central.maven.org/maven2/com/facebook/swift/swift-generator-cli/0.14.2/swift-generator-cli-0.14.2-standalone.jar

maven命令下载

执行maven命令下载swift-generator-cli-0.14.2-standalone.jar到lib文件夹下

mvn org.apache.maven.plugins:maven-dependency-plugin:2.8:get ^
  -Dartifact=com.facebook.swift:swift-generator-cli:0.14.2:jar:standalone ^
  -Ddest=lib/swift-generator-cli-0.14.2-standalone.jar

生成Client代码

java -jar lib\swift-generator-cli-0.14.2-standalone.jar ^
    TestService.thrift ^
    -generate_beans ^
    -override_package net.gdface.facelog.client ^
    -out client/java

-override_package 参数用于指定生成代码的包名,可不指定，则默认使用thrift文件中定义的package
-out 指定代码生成文件夹
-generate_beans 指定将数据对象生成标准Java Bean

生成的service端接口代码
TestService.java

package net.gdface.facelog.client;

import com.facebook.swift.codec.*;
import com.facebook.swift.codec.ThriftField.requiredness;
import com.facebook.swift.service.*;
import com.google.common.util.concurrent.ListenableFuture;
import java.io.*;
import java.util.*;

@ThriftService("TestService")
public interface TestService
{
    @ThriftService("TestService")
    public interface Async
    {
        @ThriftMethod(value = "getBean")
        ListenableFuture<TestBean> getBean();

        @ThriftMethod(value = "setBean")
        ListenableFuture<Void> setBean(
            @ThriftField(value=1,name="arg0",requiredness=requiredness.NONE) final TestBean arg0
        );
    }
    @ThriftMethod(value = "getBean")
    TestBean getBean();


    @ThriftMethod(value = "setBean")
    void setBean(
        @ThriftField(value=1,requiredness=requiredness.NONE) final TestBean arg0
    );

}

生成的TestBean.java代码

package net.gdface.facelog.client;

import com.facebook.swift.codec.*;
import com.facebook.swift.codec.ThriftField.requiredness;
import java.util.*;

import static com.google.common.base.Objects.toStringHelper;

@ThriftStruct("TestBean")
public final class TestBean {
    public TestBean() {
    }

    private int id;

    @ThriftField(value=1,name="id",requiredness=requiredness.NONE)
    public int getId() { return id; }

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

    @Override
    public String toString()
    {
        return toStringHelper(this)
            .add("id",id)
            .toString();
    }
}