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
@AllArgsConstructor
public 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;
@Data
public 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
@AllArgsConstructor
public 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;
@Data
public 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
能看到这里的同学，就帮忙右上角点个赞吧，Thanks(･ω･)ﾉ
