Mockito框架抛出NullPointerException

首先看一下Mockito框架是怎么抛出NullPointerException

比如下面的代码

Company类

package com.one.util;import java.util.List;import lombok.AllArgsConstructor;import lombok.Data;@Data@AllArgsConstructorpublic  class Company {    private String name;    public String companyList(List<Company> companies){        return companies.get(0).getName();    }}

Person类如下

package com.one.util;import java.util.ArrayList;import java.util.List;import lombok.Data;@Datapublic class Person {    private Company company;    public  Person(Company company) {        this.company = company;    }    public String test1() {        List companyList = new ArrayList<Company>();        companyList.add(company);        return this.test2(company.companyList(companyList));    }    public String test2(String name) {        return name.toString();    }}

PersonTest 测试类代码如下

package com.one.util;import java.util.ArrayList;import java.util.List;import org.assertj.core.api.Assertions;import org.assertj.core.util.Lists;import org.junit.Before;import org.junit.Test;import org.junit.runner.RunWith;import org.mockito.Mock;import org.mockito.Mockito;import org.mockito.runners.MockitoJUnitRunner;@RunWith(MockitoJUnitRunner.class)public class PersonTest {    @Mock    private Company company;    private Person person;    @Before    public void setUp(){        person = new Person(company);    }    @Test    public void show() {        List<Company> companies = Lists.newArrayList();        Mockito.when(company.companyList(companies)).thenReturn("hello");        String s = person.test1();        Assertions.assertThat(s).isEqualTo("hello");    }}

然后执行上面的测试方法show()，此时结果就会抛出空指针异常了，这是什么原因呢，我么往下看

分析上面为什么抛出NullPointerException

这是因为你的测试方法show()方法里面的Mockito.when(company.companyList(companies)).thenReturn("hello")里面的变量companies变量的地址和真正执行到Company类里面的companyList方法里面的companies参数变量的地址是不一样的，所以真正执行的时候，调用Mockito.when(company.companyList(companies)).thenReturn("hello")返回的就是null

就比如下面的companies的变量是OX001

然后当真正执行到Company类里面的companyList()方法的时候，因为test1()方法里面有重新new了一个集合当成companyList()方法的参数，此时test1()方法里面又重新new的集合companyList变量的地址就会是OX003，

然后因为show()测试方法里面companies变量的地址和test1()方法里面的new的companyList变量的地址是不同的，所以show()方法里面的Mockito.when(company.companyList(companies)).thenReturn("hello")是执行不成功的，然后就会返回null，然后因为在test1()方法里面调用test2()方法，所以此时就会抛出空指针

怎么解决这个问题呢

使用Mockito.any()就可以了
比如下面的代码

Company类

package com.one.util;import java.util.List;import lombok.AllArgsConstructor;import lombok.Data;@Data@AllArgsConstructorpublic  class Company {    private String name;    public String companyList(List<Company> companies){        return companies.get(0).getName();    }}

Person类如下

package com.one.util;import java.util.ArrayList;import java.util.List;import lombok.Data;@Datapublic class Person {    private Company company;    public  Person(Company company) {        this.company = company;    }    public String test1() {        List companyList = new ArrayList<Company>();        companyList.add(company);        return this.test2(company.companyList(companyList));    }    public String test2(String name) {        return name.toString();    }}

PersonTest 测试类代码如下，此时Mockito.when(company.companyList(any())).thenReturn("hello")里面使用的就是any()

package com.one.util;import java.util.ArrayList;import java.util.List;import org.assertj.core.api.Assertions;import org.assertj.core.util.Lists;import org.junit.Before;import org.junit.Test;import org.junit.runner.RunWith;import org.mockito.Mock;import org.mockito.Mockito;import org.mockito.runners.MockitoJUnitRunner;import static org.mockito.Matchers.any;@RunWith(MockitoJUnitRunner.class)public class PersonTest {    @Mock    private Company company;    private Person person;    @Before    public void setUp(){        person = new Person(company);    }    @Test    public void show() {        List<Company> companies = Lists.newArrayList();        Mockito.when(company.companyList(any())).thenReturn("hello");        String s = person.test1();        Assertions.assertThat(s).isEqualTo("hello");    }}

此时结果如下所示，成功了

原文链接

能看到这里的同学，就帮忙右上角点个赞吧，Thanks(･ω･)ﾉ