Struts2注解配置Action、返回Json（restful api）、上传图片转Base64

Struts2是一个基于MVC设计模式的Web应用框架，它本质上相当于一个servlet，在MVC设计模式中，Struts2作为控制器(Controller)来建立模型与视图的数据交互。Struts 2以WebWork为核心，采用拦截器的机制来处理用户的请求，这样的设计也使得业务逻辑控制器能够与ServletAPI完全脱离开，所以Struts 2可以理解为WebWork的更新产品。虽然从Struts 1到Struts 2有着太大的变化，但是相对于WebWork，Struts 2的变化很小。

Struts2的原理及特性介绍：Struts2百科

Struts2应用@Action注解写Action测试和图片转Base64显示

Struts2应用注解的同时与Spring结合会有依赖库版本冲突问题！
经测试
Spring-core 和 Spring-context 和 spring-beans 的 4.3.13.RELEASE 版本
与
Struts2-core 和 struts2-convention-plugin 的 2.5.16 版本
以及
Struts2-Spring-Plugin 2.5.18 版本
可以完美结合。
同时其它的依赖库还可以选择更高或者其它版本。

本测试使用的 gradle.build 配置。

    configurations.all {
        resolutionStrategy {
            force 'org.springframework:spring-beans:4.3.1.RELEASE'
        }
    }

    configurations.all {
        resolutionStrategy {
            force 'org.springframework:spring-core:4.3.1.RELEASE'
        }
    }
//    加入main/java目录下的*.hbm.xml打包 发布
    sourceSets {
        main {
            resources {
                //这里的srcDir是方法，上面的是属性
                srcDir 'src/main/java' //可以将java目录下的所有非.java资源打包到classes下
            }
        }
    }
    // https://mvnrepository.com/artifact/org.springframework/spring-core
    compile group: 'org.springframework', name: 'spring-core', version: '4.3.13.RELEASE'

    // https://mvnrepository.com/artifact/org.springframework/spring-context
    compile group: 'org.springframework', name: 'spring-context', version: '4.3.13.RELEASE'

    // https://mvnrepository.com/artifact/org.springframework/spring-aop
    compile group: 'org.springframework', name: 'spring-aop', version: '5.0.0.RELEASE'

    // https://mvnrepository.com/artifact/org.apache.struts/struts2-convention-plugin
    compile group: 'org.apache.struts', name: 'struts2-convention-plugin', version: '2.5.16'

    // https://mvnrepository.com/artifact/org.apache.struts/struts2-core
    compile group: 'org.apache.struts', name: 'struts2-core', version: '2.5.16'

    // https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api
    compile group: 'javax.servlet', name: 'javax.servlet-api', version: '4.0.0'

    // https://mvnrepository.com/artifact/org.apache.struts/struts2-spring-plugin
    compile group: 'org.apache.struts', name: 'struts2-spring-plugin', version: '2.5.18'

    // https://mvnrepository.com/artifact/org.springframework/spring-beans
    compile group: 'org.springframework', name: 'spring-beans', version: '4.3.13.RELEASE'

// https://mvnrepository.com/artifact/javax.servlet.jsp.jstl/jstl
    compile group: 'javax.servlet.jsp.jstl', name: 'jstl', version: '1.2'

web.xml里的struts过滤器spring-context web监听器还是要配置

    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
    
    <filter>
        <filter-name>struts2</filter-name>
        <filter-class>org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter</filter-class>
    </filter>
    
    <filter-mapping>
        <filter-name>struts2</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

</web-app>

结合Spring注解还是要在applicationContext.xml里开启一些配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
      http://www.springframework.org/schema/context
      http://www.springframework.org/schema/context/spring-context-4.3.xsd
      http://www.springframework.org/schema/aop
      http://www.springframework.org/schema/aop/spring-aop.xsd

">
    <context:annotation-config></context:annotation-config>
    <context:component-scan base-package="actions"></context:component-scan>
    <context:component-scan base-package="Repositories"></context:component-scan>
    <aop:aspectj-autoproxy proxy-target-class="true" />
</beans>

处理图片Action

开启struts2的action注解类的所在包的名字默认为 actions 。放在其它包中无法识别，对类名没有限定。

@Controller
public class IndexController extends ActionSupport  {
    private File pictureFile ;
    private String pictureBase64;

    public File getPictureFile() {
        return pictureFile;
    }

    public void setPictureFile(File pictureFile) {
        this.pictureFile = pictureFile;
    }

    public String getPictureBase64() {
        return pictureBase64;
    }

    public void setPictureBase64(String pictureBase64) {
        this.pictureBase64 = pictureBase64;
    }
    
    @Action(value="/pb",results = {@Result(name="success",location = "/Views/Test/Test.jsp")})
    public String pb(){
        return "success";
    }

    @Action(value="/ConvertPicture",results = {@Result(name="success",location = "/Views/Test/Test.jsp")})
    public String convertToBase64() throws IOException {
        if (this.pictureFile.exists()) {
            String serverpath = "E:/Picture";
            File uploadDir = new File(serverpath);
            if (!uploadDir.exists()) {
                uploadDir.mkdirs();
            }

            InputStream inputStream1 = new FileInputStream(this.pictureFile);
            byte[] data = new byte[inputStream1.available()];
            inputStream1.read(data);
            BASE64Encoder base64Encoder = new BASE64Encoder();
            String base64str = base64Encoder.encode(data);

            System.out.println(base64str);

            StringBuffer stringBuffer = new StringBuffer(base64str);
            stringBuffer.insert(0, "data:img/jpg;base64,");

            System.out.println(stringBuffer);

            this.pictureBase64 = stringBuffer.toString();

        }
        return "success";
    }
}

上传和显示图片视图页面

Test.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<img src="<s:property value="pictureBase64" />" width="200px" height="150px">

<s:form action="ConvertPicture" method="POST" enctype="multipart/form-data">
<input type="file" name="pictureFile">
<input type="submit" value="submit">
</s:form>
</body>
</html>

使用效果

进入 http://localhost:8080/BBS/pb
选择文件——>点击submit

---

Struts2返回Json对象和Json数组的方案

方案一：使用 struts-json-plugin 库

只需要添加依赖然后在Action类里使用相应注解就可以实现restful api 风格的数据了。

gradle添加依赖

    compile group: 'org.apache.struts', name: 'struts2-json-plugin', version: '2.5.16'
    compile group: 'com.alibaba', name: 'fastjson', version: '1.2.56'

action配置

struts2-json-plugin 可以返回单个对象或者是集合；比如
JSONObject、JSONArray

在使用时主要有三个点：
在action类前加 @ParentPackage(value=“json-default”)
在@Action注解里results参数里 type = “json”, params = {“root”, “resultJsonObj”}) 无论是单个对象还是集合数组都用 type = “json” 。而params需要指定为 {“root”,“类字段”} 后面的参数为类字段必须有get set 方法。

@ParentPackage(value="json-default")
public class CommonController extends ActionSupport {
  // 要返回的Json对象,params参数与变量名一致
    private JSONObject resultJsonObj = new JSONObject();
    private JSONArray resultJsonArray = new JSONArray();
  
    public JSONArray getResultJsonArray() {
        return resultJsonArray;
    }

    public void setResultJsonArray(JSONArray resultJsonArray) {
        this.resultJsonArray = resultJsonArray;
    }

    public JSONObject getResultJsonObj() {
        return resultJsonObj;
    }

    public void setResultJsonObj(JSONObject resultJsonObj) {
        this.resultJsonObj = resultJsonObj;
    }

    @Action(value="GetLocalHostIp" , results = {@Result(name = "success" , type = "json", params = {"root", "resultJsonObj"})})
    public String getLocalHostIpProc(){
        String url = null;
        try {
            url = Inet4Address.getLocalHost().getHostAddress();
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
        url = "http://" + url + ":8080";

        resultJsonObj.put("text", url);
        return "success";
    }
    
    @Action(value="listAllDirs" , results = {@Result(name="success" , type = "json" , params = {"root" , "resultJsonArray"})})
    public String listAllDirsProc(){

        List<RootDir> rootDirList= ... ;
        List<SecondDir> secondDirList= ...;
        List<ThirdDir> thirdDirList= ...;

        JSONArray rootdirjsons=new JSONArray();
        JSONArray seconddirjsons=new JSONArray();
        JSONArray thirddirjsons=new JSONArray();

        rootDirList.forEach((i)->{
            JSONObject resultOne=new JSONObject();
            resultOne.put("rootDirId",i.getRootDirId().toString());
            resultOne.put("rootDirName", i.getRootDirName().toString());
            rootdirjsons.add(resultOne);
        });

        secondDirList.forEach((i)->{
            JSONObject resultOne=new JSONObject();
            resultOne.put("rootDirId",i.getRootDirId().toString());
            resultOne.put("secondDirId",i.getSecondDirId().toString());
            resultOne.put("secondDirName", i.getSecondDirName().toString());
            seconddirjsons.add(resultOne);
        });

        thirdDirList.forEach((i)->{
            JSONObject resultOne=new JSONObject();
            resultOne.put("secondDirId",i.getSecondDirId().toString());
            resultOne.put("thirdDirId",i.getThirdDirId().toString());
            resultOne.put("thirdDirName", i.getThirdDirName().toString());
            thirddirjsons.add(resultOne);
        });

        resultJsonArray.add(rootdirjsons);
        resultJsonArray.add(seconddirjsons);
        resultJsonArray.add(thirddirjsons);

        return "success";
    }
 
}

测试结果OK

单个Json

Json数组

第二种方案，借助输出流，来向请求响应一个json格式的数据。

        Object out = new String();
        HttpServletResponse response = ServletActionContext.getResponse();
        response.setContentType("application/json;charset=utf-8");
        writer = response.getWriter();
        response.setDateHeader("Expires", 0);
        JSONObject.toJSON(out);
        writer.write(object.toString());
        writer.flush();

建议：在restful需求比较少的情况下使用第二种方案，有一定量的restful需要还是用struts-json-plugin方便。