一起学习SSM框架之SpringMVC(三)

SpringMVC

• 静态资源
• Json处理
• • 1.导入依赖
  • 2.使用@ResponseBody
  • 3.使用@RestController
  • 4.使用@RequestBody
  • 5.Jackson常用注解
• FastJson

静态资源

静态资源：HTML，js文件，css文件，图片文件
静态文件没有url-pattern，所以默认是访问不到的，之所以可以访问，是因为tomcat中有一个全局的servlet：org.apache.catalina.servlets.DefaultServlet，它的url-pattern是“/”，是全局默认的servlet，所以每个项目中不能匹配到静态资源请求的时候，用这个来处理

1.解决方案1

DispathcerServlet采用其他的url-pattern
此时，所有的访问handler的路径都要以action结尾

  <servlet>
        <servlet-name>ozl_mvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:mvc.xml</param-value>
        </init-param>
        <!--可选配置，不写就是懒汉式加载，写了就是饿汉式加载-->
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>ozl_mvc</servlet-name>
        <url-pattern>*.action</url-pattern>
    </servlet-mapping>

2.解决方案2

DispathcerServlet的url-pattern依然采用"/"，但要追加配置

   <!-- 额外增加一个handler，且requestMapping："/**"可以匹配所有的请求，
    但是优先级最低，所以如果其他所有的handler都匹配不上，请求会转向"/**"，
    恰好这个handler是处理静态资源的处理方式：将请求转会到tomcat中default的Servlet

    requestMapping："/**"    /xx/xx或者/x就是所有路径
    -->
    <mvc:default-servlet-handler/>

3.解决方案3

	 <!--
        1.mapping是访问路径，location是存放资源位置
        2.将/html/**中/**匹配到的内容，拼接到/page/
     -->
    <mvc:resources mapping="/html/**" location="/page/"/>

Json处理

SpringMVC默认的Json处理方案选择是Jackson，所以只需要导入Jackson的jar

1.导入依赖

  <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.9.8</version>
        </dependency>

2.使用@ResponseBody

@ResponseBody
将handler的返回值，转换成json(jackson)，并将json响应给客户端

@Controller
@RequestMapping("/json")
public class JsonController {
    @RequestMapping("/test1")
    @ResponseBody
    public User test1(){
        System.out.println("test1");
        User user = new User(1,"李四");
        return user;
    }

    @RequestMapping(value = "/test2",produces = "text/html;charset=utf-8")
    @ResponseBody
    public String test2(){
        System.out.println("test2");
        return "利好";//结果返回 利好
    }
}

3.使用@RestController

@RestController
给该控制类的所有方法即handler都加上@ResponseBody的作用
注意：使用了@RestController可以不用写@Controller，因为@RestController里面已经有了@Controller注解

@RestController
@RequestMapping("/json")
public class JsonController {
    @RequestMapping("/test1")
//    @ResponseBody
    public User test1(){
        System.out.println("test1");
        User user = new User(1,"李四");
        return user;
    }

    @RequestMapping(value = "/test2",produces = "text/html;charset=utf-8")
//    @ResponseBody
    public String test2(){
        System.out.println("test2");
        return "利好";
    }

    @RequestMapping("/test3")
    public String test3(@RequestBody User user){
        System.out.println(user);
        return "ok";
    }
}

4.使用@RequestBody

@RequestBody 接收json参数

4.1定义handler

实体类User

public class User {
    private Integer id;
    private String name;
    private Boolean gender;
    private Date birth;
    private String[] hobby;

    public User(){

    }
    public User(Integer id, String name) {
        this.id = id;
        this.name = name;

    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", gender=" + gender +
                ", birth=" + birth +
                ", hobby=" + Arrays.toString(hobby) +
                '}';
    }

    public String[] getHobby() {
        return hobby;
    }

    public void setHobby(String[] hobby) {
        this.hobby = hobby;
    }

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Boolean getGender() {
        return gender;
    }

    public void setGender(Boolean gender) {
        this.gender = gender;
    }

    public Date getBirth() {
        return birth;
    }

    public void setBirth(Date birth) {
        this.birth = birth;
    }
}

JsonController

 @RequestMapping("/test3")
    public String test3(@RequestBody User user){//@RequestBody将请求体中的json数据转换为java对象
        System.out.println(user);
        return "ok";
    }

4.2Ajax发送json

下载jquery-2.1.1.js的代码导入进去

json.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
    <script src="${pageContext.request.contextPath}/js/jquery-2.1.1.js"></script>
</head>
<body>
    <input type="button" value="ajax" onclick="send_json();">
    <script>
        function send_json(){
        //    ajax json
            var user={id:1,name:"战三"};
            var userJson=JSON.stringify(user);

            $.ajax({
                url:"${pageContext.request.contextPath}/json/test3",
                type:"post",
                data:userJson,
                contentType:"application/json",
                success:function (ret){
                    alert(ret);
                }
                }
            )
        }
    </script>

</body>
</html>

5.Jackson常用注解

5.1日期格式化

@JsonFormat(pattern=“yyyy-MM-dd HH:mm:ss”)

User

    @JsonFormat(pattern = "YYYY-MM-dd HH:mm:ss",timezone = "GMT+8")
    private Date birth;

JsonController

    @RequestMapping("/test1")
//    @ResponseBody
    public User test1(){
        System.out.println("test1");
        User user = new User(1,"李四",new Date());
        return user;
    }

5.2属性名修改

User

 @JsonProperty("id_new")
    private Integer id;

json响应的id属性变成id_new

5.3属性忽略

User

 @JsonIgnore
    private Boolean gender;

json响应就不会有gender属性

5.4null和empty属性排除

@JsonInclude(JsonInclude.Include.NON_NULL)
null值，属性不输出
元素为空就不会json响应显示

@JsonInclude(JsonInclude.Include.NON_NULL)
    private List<String> hobby;

@JsonInclude(JsonInclude.Include.NON_EMPTY)
empty属性不输出（空串，长度为0的集合，null值）

 @JsonInclude(JsonInclude.Include.NON_EMPTY)
    private List<String> hobby;

5.5自定义序列化

User

  @JsonSerialize(using= MySerializer.class)
    private Double salary=10000.262; //用MySerializer输出

    public Double getSalary() {
        return salary;
    }

    public void setSalary(Double salary) {
        this.salary = salary;
    }

MySerializer

public class MySerializer extends JsonSerializer<Double> {


    public void serialize(Double aDouble, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
        //将salary的值四舍五入  留两位小数
        String number= BigDecimal.valueOf(aDouble).setScale(2,BigDecimal.ROUND_HALF_UP).toString();
        //输出四舍五入的值
        jsonGenerator.writeNumber(number);
    }
}

FastJson

SpringMVC默认的json处理方案是Jackson，但是FastJson性能更好，可以使用FastJson处理方案

1.导入依赖

 <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.47</version>
        </dependency>

2.安装FastJson

mvc.xml

 <!--启动mvc注解驱动-->
    <mvc:annotation-driven>
        <!--安装FastJson，转化器-->
        <mvc:message-converters>
            <bean class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter">
                <!--声明转换类型：json-->
                <property name="supportedMediaTypes">
                    <list>
                        <value>application/json</value>
                    </list>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>

3.使用常用注解

日期格式化：@JSONField(format = “yyyy/MM/dd”)
属性名修改：@JSONField(name=“xxxx”)
忽略属性名：@JSONField(serialize = false)
包含null值：@JSONField(serialzeFeatures = SerializerFeature.WriteNullStringAsEmpty)
//null的String输出为""空串
@JSONField(serialzeFeatures = SerializerFeature.WriteMapNullValue)
//默认会忽略所有null值，有此注解输出null
自定义序列化： @JSONField(serializeUsing =xxxx.class)

User2

public class User2 {
    @JSONField(serialize = false)
    private Integer id;
    @JSONField(name="Name",serialzeFeatures = SerializerFeature.WriteNullStringAsEmpty)
    private String name;
    @JSONField(serialzeFeatures = SerializerFeature.WriteMapNullValue)
    private String city;
    @JSONField(format = "yyyy/MM/dd")
    private Date birth;
    @JSONField(serializeUsing = MySerializer2.class)
    private Double salary;

    public User2(Integer id, String name, String city, Date birth, Double salary) {
        this.id = id;
        this.name = name;
        this.city = city;
        this.birth = birth;
        this.salary = salary;
    }

    @Override
    public String toString() {
        return "User2{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", city='" + city + '\'' +
                ", birth=" + birth +
                ", salary=" + salary +
                '}';
    }

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public Date getBirth() {
        return birth;
    }

    public void setBirth(Date birth) {
        this.birth = birth;
    }

    public Double getSalary() {
        return salary;
    }

    public void setSalary(Double salary) {
        this.salary = salary;
    }
}

MySerializer2

public class MySerializer2 implements ObjectSerializer {
    public void write(JSONSerializer jsonSerializer, Object o, Object o1, Type type, int i) throws IOException {
        Double value=(Double) o;//salary属性值
        String text=value+"元";//salary属性值后面添加 元
        jsonSerializer.write(text);

    }
}

JsonController

  @RequestMapping("/test12")
//    @ResponseBody
    public User2 test12(){
        System.out.println("test12");
        User2 user2= new User2(1,"李k","上海",new Date(),1000.22);
        return user2;
    }

本文地址：https://blog.csdn.net/ozl520/article/details/109225107